"BL is just boy x boy romance, can be pure and innocent."
Look, if you want to lie to yourself, then that's fine, but don't lie to me. Even the most tame romance stories will get some hardcore fanfics, AUs, doujin comics, and whatever else fans want. Reading BL is going down the rabbit hole, and she's already in a site known for having tons of smut.
Oh come on that’s not fair. In that case any romance story is going down a rabbit hole. I’m sure one can simply avoid stories tagged as mature or smut. I read fanfics growing up and I avoided the “lemon” fics easily. On AO3 too, infamous for its depraved tags.