If she chose to suck dikk while you're at work, she is not in need of protection. For all you know, 8maybe the daughter told him you were cool with it. Just like "that's a whole man", she's not a little girl anymore either. Her choosing to spread her legs is a grown woman choice.
If an adult touches my son, cause he did something against a girl's will, I'm telling my son to hold his own nuts. But if the girl was willing and her dad touches my son, i guarantee the dad will end up in the hospital.