What an interesting thread! I agree with everybody 
My "what if"s are only two, very fundamental things:
If I'd had Mumsnet, I would have been less confused & susceptible to my abusers' methods.
If my parents had had a healthy relationship, I would have been open to non-abusive partners. As it was, I didn't recognise them. I thought all relationships were abusive.
But my boundary issues aren't everybody's. Loads of people with genuinely solid, emotionally healthy families also fall prey to abuse, despite having all the good templates. Loads of psychotherapists, DV workers and divorce lawyers are abused, despite knowing all the facts and patterns. And many of them put up with abuses I wouldn't have tolerated, because they are not me and vice versa.
Much of what we want to characterise as vulnerability to abuse is simple, human vulnerability. You can't have intimate relationships without showing your vulnerability (I'm not preaching here, I'm well aware that I'm destroying my own chances of intimacy through fear!) You can't love and be loved without compassion. Emotional honesty and compassion are wide open to abuse, but we can't function fully as people without them or while hiding them.
I agree the supposed cleverness of abusers is all in the eye of the beholder. Since the majority of abusers begin by exploiting their targets' good qualities, however, and undermining their judgement, every abuser is clever. Each abuser cleverly gets to know his/her target's strengths and cleverly manipulates them into weaknesses. By the time a target comes to us, she truly believes her abuser is exceptionally clever. because that's an intended effect of the abuse.
All children should, in my very strong opinion, be taught properly about relationship dynamics both good & bad - Freedom Programme style - and also about interpersonal respect, rights & responsibilities. They should be taught assertiveness. All adults who suffer abuse should be properly taught these things, as well.
But there will still be abusers, and there will still be targets for them - because abuse is no more or less than distorted love. And, if we want love, we are vulnerable.
Essay, sorry 