Lemmy and Kbin have both seen a huge influx of people in the past few weeks, so admins of each instance are struggling to keep up. For the most part, the admins are working for free, in addition to whatever their day jobs are.
Having said that, I'd report those magazines / communities to the admin of the instance for action, understanding that right now, they're buried in requests, questions, and complaints. If the issue is an entire instance, well, defederation is an option.
FWIW, I was threatened on Reddit more than once with actual murder... people threatening to come to my house and kill me. Reddit's general response was to... delete the chat message in question as a "resolution" to my complaint. AFAIK, that was the extent of their action. I at least have the impression that abusive users will be removed, though it might take a bit given the incredible influx of new users.
I am sorry that they're harassing you though. Noting to block those magazines / communities.