Frankly my position on it is, “Don’t write the hate in the first place.” It’s entirely possible to communicate a thoughtful critique or even flat-out disapproval of a concept without being mean and hurtful.
Let’s use Tunalock as an example, because it’s minimally emotionally loaded but gets a lot of hate. If you personally despise Tunalock, like nails-on-a-chalkboard “Get it away from me,” and you want to post about that: it’s your blog, so go ahead and post. But that’s entirely a personal dislike, and there’s no reason to go tagging it and thrusting it under the noses of people who like it.
On the other hand, if you think Tunalock as a concept is problematic, and you’re concerned about depictions of animal abuse or whatever, then that’s something that IS worth communicating to the people who participate in it. If you’re right and they’re overlooking the fact that their AU has problematic elements, then that’s a dialogue worth having.
But in that case, you are trying to start a dialogue. You want to engage with these people, and teach and learn (at the very least, it’s worth listening to how others see a problematic concept, so that you can understand and get to the root of the issue). So if you want to write a post about that and tag it in, you want to write it in a way that invites approach and engagement. There’s no call to be hateful in that scenario; you’re there to open a discussion. Here, watch:
“Hey, guys. I keep seeing these Tunalock pictures sail across my dash, and they kind of worry me. To me this looks like bestiality or animal abuse, and I’m concerned about it.”
And then you can leave it at that, if you just wanted to air your thoughts—because you’ve explained what worries you, and it’s a legitimate worry, and you’re not accusing them of being history’s greatest monsters just because they have a maybe-problematic thing they like (who doesn’t have maybe-problematic things they like, really?).
Or if you want more information or discussion, you can simply ask for it. ”Can you explain this to me? Do you have any thoughts?”
Now, just because you’ve been polite doesn’t mean that every response you get will automatically be the same. Some people are rude. And people in a community that has experienced attack before are likely to be defensive and automatically jump toward the less gracious interpretation of your words, if one is available (in which case, try to understand that, and politely clarify if they’ve read you wrong.)
But in general, I’ve found that being forthright, respectful, and prepared to listen before I jump to conclusions heads off the majority of potential wank, when I find it necessary to stick my foot in somebody else’s pool.