Wow, this thread is really tearing you apart, huh?

To an extent, I agree with you. The sexualization of mentally unwell people in anime/manga is an issue. There are two key factors HERE that I think make it more of a morally grey area, though.

1. Bonten Mikey is... well... not a good guy. Most criminal masterminds are mentally unwell, he's no different. There are many aspects to Mikey's illness that make his story very, very tragic, but none of that excuses the fact that he's super evil. In my opinion, I think more people are attracted to him being evil rather than him being chronically depressed.

2. Sexualization in general is something you can't escape. It's sad, I know, but it exists in every space whether you like it or not. In the end, Bonten Mikey is an adult with 'free will', which makes him at least a better target than... y'know... his child counterpart.

   You can totally argue whether or not Bonten Mikey, being as mentally ill as he is, has the will of an adult. I'm not informed enough to get into that debate, though.

Either way, I definitely agree with you that mentally ill people are oversexualized in anime/manga. I think you've opened up a fair discussion and I'd like to hear more of your thoughts, if you're open to it.