I'd say the problem is that Comic Sans is already an established meme. Everyone who knows what Comic Sans is already knows that it's bad, and a design smell, and you absolutely positively should never ever use it for anything. Of course, the little know secret that was just brought up here is that no one really knows why. It doesn't matter to them. There are some good reasons to restrain yourself from using that font in some situations, but current attitude towards Comic Sans is pure fashion.

It's the exact same situation as programmers have with goto - there's this widely established meme of "goto considered harmful" that most have heard somewhere, but have no clue why it's so except that it is. Only few of us know why using goto leads to bad consequences (and what those consequences are); even fewer could name situations where goto is a right tool for the job. For the rest, it's fashion.