In that sense, I don't know that comparisons to rates of sexual abuse would be all that helpful, since it would only represent a part of the picture.

I don't think anyone is proposing that this is the one factor that leads to BLism. It is expected that if this contributes to the creation of BLs, then it is likely to be only one of the many factors that contributes to that. This is why we shouldn't look for a one to one relationship between increases in broken homes and increases in child abuse. But if a relationship between the two things really does exist, and there is a dramatic increase in broken homes, then there should also be a (much smaller, but still statistically significant) increase in child sexual abuse. Of course other factors still influence it, but a dramatic change in that factor should be reflected, even if only to a small extent.