It's just about the timing and choice of person you go preachy on is all.
I do not give a damn about your dietary preferences. At all, in the slightest.

And so who do you choose to annoy? Obviously the person saying vegans aren't the worst, but just "people".

It's like you're trying to persuade people that they're wrong when they say that vegans, like all people, have a range of "chill" to "insufferable".

Don't worry though, you have not shaken my beliefs. I just think you in particular are insufferable on this topic.