Have we become more intelligent over the last 2000 years? Sure, we’ve gained knowledge and developed technology, but are you and I more intelligent than Cicero or Plato?
I don’t see why they’d equate us with insects. We don’t equate primitive tribes of humans with insects. We don’t think of the Ancient Greeks as insects.
They’d have better technology (else they wouldn’t be here) but they won’t necessarily be more intelligent.
Taking into account the Fermi Paradox (i.e. oh yeah, then where the hell are they?!?), I tend to go low on Drake equation estimate. An average of less than one advanced civilization per galaxy is about right. I just don’t buy a Star Trek or Star Wars type situation with alien beings constantly bumping into each other, giving each other shit, like K-Mart shoppers during a Blue Light Special at Christmastime.
With this in mind, once a species has climbed to the apex position on its home planet, via survival of the fittest tactics (violence, cunning, Donald Trumpism, etc. ), it can afford to take a number of eons out chilling, mellowing, devolving violent dispositions and growing brains big enough to negotiate interstellar travel. These are the super-intelligent beings that we are likely to encounter once they take the intellectual/technological leap from interstellar to intergalactic travel. With all their bad temperament bred out of them during the non-competitive years, they’ll be as gentle to us as cat ladies are to their tabbies.
Super-Intelligent Beings = Pussycats
The ones to fear are the Super-Duper-Intelligent Beings. These are the cats who regard traveling to distant galaxies on par with skateboarding to the corner 7-11. They will have a history of bumping into a cornucopia of advanced civilizations and will have re-evolved violent dispositions in order to subdue them. You don’t want to meet one of those pussies in dark alley.
Super-Duper_Intellegent Beings = Bad Ass Cats
We do if they have something we want. Look how we treat other humans that we don’t think are as civilized as we are or just look slightly different.
And, another thing…! 
There seems to be a meme to the effect: we’re pretty close technology-wise to any other advanced civilization who could not only visit us, but threaten us—after all, we’ve put a probe on Titan.
Balderdash.
Placing a probe on a celestial body orbiting a non-local star must be an order of magnitude more advanced than placing one on a local moon. Executing a successful military campaign against the apex species of a planet orbiting a non-local star must be orders of magnitude more advanced than even that. It’d be like saying Mariel boatlifting a number of Cubans onto Florida soil is like Ricky Riccardo singlehandedly bringing the United States to its knees.
We’re nowhere near being in the same league as any civilization who may visit and conquer us.
We used to treat them worse (remember the Inquisition, gladiators, and slavery?), and we treat them better every decade. We’re not there yet, but we’re getting there. Civilization trends towards compassion. Now most of the world has eliminated the death penalty and is considering gay marriage if it hasn’t enacted it already.
There is an alternate scenario; interstellar travel is very difficult, and can only be acheived with great effort.
Because of mass considerations a spacecraft that arrives from another star (using any propulsion system we can currently imagine) would be very small and cramped by the time it finally decelerates to orbital speed, or will have taken thousands of years to get here. In either case the occupants of said craft might be in very poor physical and mental shape. They might need our help more than we need theirs; they may be in no fit state to conquer anyone.
This is like one of the two scenarios I keep imagining: that an non-humanoid alien civilization lands in some remote corner of the Earth (granted, those are getting harder and harder to find) and basically goes about its business (e.g. cultivating some obscure Earth fungus that they use as an appetizer). We visit them in force to see what their intentions are, only to get an annoyed “Get outta here, kids, ya bother me,” in response. They simply have no interest in us.
Scenario #2: A intelligent-machine culture lands on Earth, looking for the AI that has undoubtedly spread itself across the planet. However, none of the signals that it exudes can be translated into meaningful dialog…
“What is this, 10011101? I can’t get this guy to say anything! Is he ignoring us?”
“I don’t know, 11001100. And what are all these carbon-and-water-bags shuffling around all over the place?”
“Beats me. Maybe it’s some kind of fungus. They’re ugly and they give off unpleasant odors.”
Why? If you and I are both members of a climbed-to-the-apex-with-the-cunning-tactics-of-Trumpism species, and one of us chills and mellows while the other keeps on with the cunning tactics of Trumpism – well, look, that’s a good move for the latter and a bad move for the former, right? So why would either of us abandon it?
Only because you judge “valuing life” as a matter of some absolute importance. I would not describe most aggressive behavior at the level of species, interspecies or intraspecies, as mindless in that way. It is directed, it is discussed, and those discussions take place with people not under the influence of fight or flight responses.
When people are starving, we expect them to throw a lot of social niceties out the window. This is not acting mindless. It is starving.
What would bring an advanced species here? This is the question that is always brushed away. The aggro crowd seems to assume that the only reason for someone to be out and about would be for the taking, and then nothing will stand in their way. You are correct that their advances would require an intelligence superior to ours, and possibly a kind of morality that could also be considered “elevated,” but any species that would not kill to preserve itself in the face of resource shortages will never make it off their own planet. Life has no shortage of cooperation, even between species, and it is unfortunate that not enough attention is given to mutual aid; but neither has it a shortage of apathetic killing.
I would suggest that for a non-machine based intelligence the highest priority would be to discover and make available real estate. Thus they would have a directive to cleanse a location of biological infestation. The intelligence of that infestation would be of no consequence.
This touches on my view of ETs and why I question speculations of the type proposed by the OP. An alien race will by definition be alien. Ascribing motives aggressive or benevolent based on how we would behave is to anthropomorphize them. It is natural to do so because we really don’t have any example of intelligence that aren’t basically human.
It reminds me of when I was a kid and my teacher gave the assignment of drawing a picture of an alien. I realized I couldn’t because all of the tenticles, teeth extra eyes etc. I could think to give it were basically drawn from animals that exist here on earth, while an alien would have attributes that were beyond the scope of my experience and so beyond the scope of my imagination.
Now it is possible that there are certain aspects of intelligence that are universal (no pun intended), but without a second example it is hard to tell which of our attributes fall into that category, and which are specifically human/earth based.
We don’t know how rare planets like Earth are - both sufficiently massive and within the Goldilocks zone. And if aliens do want our planet, I expect the first thing we’ll know about it will be a massive meteor bombardment to sterilise the planet for them.
But have you ignored an alternative: trade? For example, Earth may be the only planet which can host a certain plant which produces a certain chemical which is useful to them.
O, I dunno, a bunch of meteors wouls burn up the atmosphere and leave the planet a flaming hell. If the aliens accept MY proposal, they would use a biological agent tailored to kill all human males (except me) and all females below a certain, er … hotness level.
Seems to me interacting with an alien biosphere is a gigantic risk. Either your microbes wipe them out or their microbes wipe you out, but somebody is getting wiped out.
This is not clear. Their microbes haven’t evolved to take advantage of our biology so they may not be able to affect us at all. Its possible that microscopic parasites or single celled organisms like bacteria could be a problem, but we wouldn’t have to worry about viruses.