Wolfgang...I've only one tiny pick to make on your great post.

"For instance we still allow males as teachers though we know that the relative risk increase is very high compared to female teachers for the absolute risk increase is still low. By far, most teacher perpetrators (sexual abuse) are males but also by far most male teachers are not perpetrators.

So even a higher relative risk alone is usually not used as a basis for discrimination (in this example, of male teachers). I have seen no good argument from Ake why it should be used in this particular case (male foster couples)."

The difference Wolfgang is in the environment.
I accept that some teachers may abuse their pupils, but the risk is drastically reduced by the classroom environment and the oppertunity of the child to discuss any attempted abuse with his/her peers without the coersion of the abuser.

When a child is introduced into a very private environment under the complete control of two male abusers the risk soars dramatically.

This may seem a simplistic point to you, but I feel its an important difference ...Ake