The father is "retarded" w/ mentality of a "7 year old".
Mother is trying to stop visitation based on fathers retardation.
I googled but was unable to fine anything regarding sexual assault on the retarded. Bay (1) Force or coercion is used to accomplish the act and the defendant is armed with a weapon or any article used or fashioned in a manner to lead the victim reasonably to believe it to be a weapon; (2) The defendant causes bodily injury to the victim; (3) The defendant is aided or abetted by one (1) or more other persons; and That's a valid question, and one that a prosecutor or court would have to evaluate if somebody tried to initiate charges.
It should be recalled, though, that mental handicaps are not necessarily equal in effect across all aspects of cognition or behavior.
He's very good looking, he's musically talented, he writes very creative works of fiction, yet he is acutely aware of his low intelligence and is quite insecure about it. I'd hate to think anyone would judge him based on his IQ alone. EDIT: At the time I wrote this, there were 7 existing answers, only one of which was good and another decent.