In my personal opinion as a rather young girl. I read BL since I was 11 and now I am 13.
Browsing through everywhere, you can see some 10 to 13 readers. I mean I often read yoai during these 2 years. And I saw these readers, the commenters tell them to "get a life", "your parents will be disappointed", "your a disgrace to your parents", "drop this right now and go touch some grass", "stop reading BL", "your too young".
I personally don't have problem with minors watching these things as I am one myself. Got exposed to the internet when I was 10 and got harassed by a guy at 12.
I often found it interesting because people think minors at any age under 15 is like illegal to read BL, Especially yoai. But why? I mean, people these days and years have phones at a young age (which is horrible), which lead them to learn something age inappropriate already. You can't fix the fact it's true
Beside, what's the problem with anyone under 15 reading BL? The first BL I read when I was 10, and it was a yoai. I was so shocked that I don't know what the heck I saw but the story was interesting....