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”.
This is not exclusive to Lemmy, this happens the same way in real life - when you critique their food choice people tend to get in the defensive. This happens whether it’s about their health, ecology or ethics and of course it gets worse when you are implying that their choices hurt others.
Of course this is not exclusive to food. Everything that is seen as part of your identity leads to this defensive reaction (see politics, sports teams etc.) and they double down on their current stance. I bet vegans would be a LOT more successful if they would be more empathetic toward non-vegans and would approach this topic more tactically.