Yes. As an admin of an instance who really doesn’t want child porn on my server, I’m gonna defederate the shit out of any instance that doesn’t take care of such content in a reasonable time. And in my opinion, loli is child porn, so defederating there as well.
Other than that, anything that’s illegal in my jurisdiction.
And the last category, spam and bigotry. Basically anything that puts too much work on my plate - if I get dozens of reports a day for users of a single instance (and I agree with the reports), I’ll defederate, because no one’s paying for my time.
So these are some valid reasons for me to defederate. There are probably more.