And in my opinion that's fine, I can honestly understand the vegan view point, and how frustrating it is to see other living beings being exploited for our gain. There is a difference between what you are describing and people who make every effort to make snotty self righteous remarks every chance they get.

At that point it isn't even about the movement anymore, it's about the individual saying these things to feel morally superior to others. They are not helping by reminding their friend that is eating an ice cream that the cow was kidnapped and raped unprompted. They gain nothing by doing that except boosting their own ego and likely making their friend unwilling to hear their view point in the future.