I might be missing something, but is it the case that we won't be able to discuss veganism? I'm vegan for ethical reasons so I do get where you're coming from with this, but I think there might be perspectives you're not seeing.
I became vegan something like six years ago and prior to that I was vegetarian for my entire life. I was vegetarian because I had a moral problem with killing things. I became vegan because I eventually ended up actually listening to vegans' arguments for why dairy etc. aren't hugely different morally speaking from meat. If you want to create more vegans - and thereby reduce suffering - vegetarians are probably some of the most receptive people to these points, assuming they don't get alienated.
Assuming I'm not missing something and it is the case that we'd be able to have friendly discussions with people about why we believe veganism is a better moral choice, I don't really see what's so wrong here.
I honestly can't recommend anyone to try psilocybin (in a safe and comfortable setting, with someone you know and trust who has experience with it) enough.
As well as being just an incredibly fun experience, it's incredibly potent as an agent for processing trauma or working on self-improvement. It also seems to be pretty powerful as an anti-addiction drug. I went from smoking about 15 a day to quitting overnight after a trip which I went into focussing on wanting to quit smoking, partly this was due to the processing I did while tripping but also I didn't really feel the normal withdrawal symptoms or cravings for a couple of days after which really helped.
I'm glad the prohibition on research/medicinal use of shrooms seems to be rolling back globally. There are some real risks involved in taking them recreationally and it's great to have such a useful tool available to people who don't want to get involved in that kind of thing!