Check the bottom post comments and see for yourself how many are self proclaimed non vegans. That post was not a discussion among peers who want justice for the animals. Just check the same type of discussions on other vegan forums, the arguments vegans make against feeding animals a meat diet is very different to what was presented in that topic.
It shouldn't matter how controversial a post is among our community, we are here for the same reason and should strive to push the animal movement forward.
Coming at this question as a member of Lemmy-at-large, and neither a vegan nor a member of your community:
(1). As your community gets larger and more active, more people will choose to block your community rather than downvote everything from it. Also, with more members their downvotes will matter less.
(2). Move your community to a different instance that is more favorable towards Veganism, such as Slrpnk or Hexbear, or self-host. Some of these instances even turn off downvotes.
What do you mean posts being hidden? That second topic seemed to be heavily disliked. It wasn't just downvotes, the comments make it clear people strongly disagreed with the topic bordering animal abuse.
I’m not certain about mods, but at least admins can see where votes are coming from, so they would have the ability to verify whether these are indeed federated vote brigadings.
Have they changed the code? Lemmy/Kbin doesn't have downvotes. The reduce (down arrow) is only supposed to help users filter content by "show me less of this content" type button. Like a step before blocking a community, but on a user level.
Also, anyone should be able to see who boosts, reduces, or favorites a thread. It's listed under "activity" on the post itself.