I've been interested in the degree to which this is true, so I did a sample of some other boards. I always picked the first thread per board to avoid cherry picking results.

• /fit/ had a dick size thread that obviously turned sexist
• /mu/ had a kpop thread, it seemed okay
• /an/ had a big cat general with nice photographs in it :)
• /g/ had an AI chatbot general. I only skimmed the beginning and that already had outright pedophilia in it.
• /a/ had an Evangelion thread with a mix of genuine discussion and softcore coomer pics of the underage girls in it
• /c/ was just cute pics of an anime girl
• /int/ discussed taking showers surprisingly
• /his/ had a thread about Anne Frank, with some users posting antisemitic content and others pushing back against it

After those I got tired. Overall I'd say the SFW boards are a very mixed bag, with some of them actually being nice.