Honestly I've never encountered anything like this even though it's constantly referenced on the Internet. Most times I only found out that people were vegan/vegetarians because we went to restaurants or something like that and they asked whhether there was any meat in a certain meal.
On the other hand, I know people who laugh about about vegans/vegetarians at every possible opportunity. Not that I have a problem with that, except if the jokes are bad

, but the stereotype of vegans stuffing their eating habits into everyone's face really couldn't be more wrong according to my personal experiences.