People consider vegans on Lemmy as too preachy. Even in vegan communities here, mods have to remove soooo many inappropriate comments (I read a few of these and they keep getting removed for good reasons). Comments that suggest going vegan on posts about animal abuse are downvoted.
At the same time, whenever there is something about Windows or Chromium based browsers, people here are doing exactly the same. “Just use Linux/Firefox/whatever”.
With “use Firefox” people tend to interpret as “try this thing instead, it’s better or will do the thing you’re looking to do”
With “go vegan” people tend to interpret it as “you’re doing something wrong and need to change your habits”.
Essentially, one is seen as a suggestion and the other an attack.