This is a rather poor way to look at it.
It's not that we're "fine" with AMW having sex with trafficked girls, it's that - as far as we know at time of writing - there is little hard proof of that beyond he said / she said and innuendos in emails. A number of people involved are now deceased. Securing a conviction on this basis would be nigh on impossible.
It is going to be orders of magnitude more difficult to convict him of a sexual offence than it would be for this where the evidence is (apparently) from the horses mouth by way of his own emails.
Unless video footage is found or some sort of inadvertent confession from Andrew e.g. by way of an old email, I think it highly unlikely any prosecution for a sexual offence would even make it to court, let alone succeed.
None of that means what he did was OK.