I'm sorry but y'all gotta accept that not all autistic special interests are cute things like trains or sanrio characters or bunny species or how rainbows work.
Sometimes an autistic person is a 45 year old man who collects world war 2 memorabilia and can name any type of bomber plane.
Sometimes an autistic person can go into extreme detail about how the human reproductive system works because it fascinates them and can tell you from memory how the process of birth goes.
Sometimes an autistic person is a goth girl who has spent her whole life researching banned medications that they used to test on people in psych wards, maybe they even own samples.
Hell maybe that autistic person is me, who watches footage of rabid animals and rabies documentaries in her free time.
And as long as you are respectful to any victims, and respect people's triggers, there's nothing wrong with this at all. Let people be autistic and be fascinated by bad things. As long as they're not being a bad person about it it's fine