I feel the same way too. The WK team can write anything they want into their program, it’s their property. However, I can’t help but feel somewhat uneasy when I read the grosser mnemonics. Have you checked out the userscript that allows you to hide mnemonics? [Userscript] WaniKani hide mnemonics
I also find some of the more violent mnemonics slightly disturbing, but often just come up with my own if they bother me too much. The only one I really had a problem with was for 鉄 (iron). The reading mnemonic encourages you to watch the trailer for the movie “Tetsuo the Iron Man”, simply describing it as a “wacky” Japanese movie. Turns out it’s a super graphic and gory (though low-budget and cheesy) horror movie! I did send a suggestion to Tofugu that they let people know about what they might see and they were happy to add a warning to the entry.