What is the name of this logical fallacy?

It reminds me of the fallacy of the excluded middle but it’s more specific than that and relies on something analogous but still different I think:

What do you call it when someone says: “You’re not in favor of my particular option so you’re in favor of nothing at all.” That is, trying to portray one’s opponent as being in favor of no standard or no action because he disagrees with one particular standard or action.

Example 1): If you’re not in favor of restricting marriage to a man and a woman, then a man will be able to marry a dog.

Example 2): If you don’t want this state intervention in the economy, then you want to leave it all up to the market.
Now, it is possible that someone who is not in favor of restricting marriage to a man and a woman would indeed want no restrictions so that a man could marry a dog. It’s also possible that someone who is against a particular intervention is against all of them. Yet it doesn’t logically follow. It’s as fallacious as saying that because someone is against the Westminster parliamentary system, they’re against all government.

So, does it have a name? It’s not really about there being a middle or denying that there is.

Hobson’s Choice is the one that I’d say, although apparently to use it for a fallacy is possibly not accurate.

Although your actual first example is more like slippery slope thinking and your second one is a false dilemma, IMO.

False Dichotomy mixed with Slippery Slope.

First off, let me mention that the hypothesis of excluded middle is not a fallacy. It is not appropriate in all situations, but gives a perfectly consistent logic. I don’t know if your examples have a name. I would call them fatuous. Maybe “false generalization”. People who made such statements are rarely worth arguing with.

I think it was Scalia who, in a dissent from overturning a Texas law outlawing homosexual behavior between consenting adults claimed that next they will want to allow gays to marry. Within a decade he was right.