http://www.veganoutreach.org/articles/youngmatt.html

The main problem ultimately is that of legitimizing a stereotype by reacting to it. By reacting to it, you're controlled by it and you've in effect said that, yes we all agree, that stereotype is real and worth condemning.

The vegan misanthrope stereotype ties into the positivity cult and this world now where showing unhappiness at all is verbotten.

Another stereotype is that of the elitist, where the rightwing has tried to make 'intelligent' a synonym for 'arrogant elitst'. Politicians have reacted by taking great pains to not sound particularly intelligent thus legitimizing the stereotype and now being controlled by it.

And so today in our society, intelligence is a bad thing and if you're not smiling, you're wrong.

It's furthermore a particularly bad idea when it comes to vegan activism in that the sort of people who become ethical vegans are thoughtful enough that they aren't basing their decision on how much you're smiling. Instead ethical vegans are left hiding much of what they really feel while trying to pander to people who couldn't actually care less about veganism no matter how they act.