Name for this annoying rhetorical device?

It has to be one of the laziest arguments/put-downs in the history of human communication: “Don’t you have anything better to do than blank?

Mundane example: You criticize a Youtube video in the comments section. Person replies “Don’t you have anything better to do than sit at your computer criticizing other people? Why don’t you do something constructive for a change?”

Is there a name for it? Is it in fact a logical fallacy, or just a rhetorical device? Of course there are a million simple ways you can dismiss this argument, but it would be nice if there were some simple term you could throw back that would encapsulate all of them (besides “You’re an idiot,” which hardly ever works :D).

I mean, I can only work on curing cancer and feeding the hungry for 10 or 12 hours a day, which leaves plenty of time to browse comment sections and explain to you why you’re wrong.

Wow, at my age I can only work on a cure for cancer a few times a week.

It seems like a simple ad hominem to me. They’re dismissing your argument by making a judgment on your character (“you have no life”) rather than arguing against the logic. That is, of course, assuming you were making a reasoned criticism and not just saying “you suck.”

It could also include the fallacy of false dilemma - i.e. that the choices are as simple, and as limited as:
a)Cure cancer, or
b)Criticise Youtube videos.

However, and as an aside, I think you might have picked better examples - judging by my experience of critical comments on Youtube*, the majority of the people posting them should indeed find something better to do, although there might not be anything they can do better.

*Second only to Yahoo Answers in terms of drooling, pointless idiocy.

Yeah, in my experience on YouTube, this type of argument is only used as a response to someone who has clearly showed they are full of themselves or posting to be an asshole.

Though if you do see it used to stop a logical criticism, try this response “As you should probably have something better to do than to criticize me. Funny how we all don’t do the best possible thing, now isnt’ it?”

It is not a logical fallacy. A logical fallacy is a flaw in a formal line of reasoning. This criticism is not a line of reasoning or an argument at all, it’s just a judgmental knee-jerk reaction.

I suppose it could be considered a rhetorical device but I don’t know if it has a name.