Consider the absurdity of that statement for a second.
How can a non-vegan ask a question about the lifestyle without engaging in a debate? How do you actively interact with information without debating it?
Debates don’t have to be antagonistic. When both parties are genuinely interested in questioning their own values and opinions they can be incredibly rewarding. I can understand a rule against antagonism, but disallowing debates inherently precludes honest questioning for people interested in growing their knowledge on the lifestyle.
Sounds like you should get involved with PTs, they’d be right up your alley. The spirit is alive and well.