I will not rehash what others here have already said, but plain I think you are missing a key point to your argument. That is any anti movement can say 'because of the possible abuse of X than we must outlaw it" that can be used for anything from anti-gun people to anti-birth control people or from anti-abortion people to anti-religion people. The fact is you can't prove a negative, so there will always room for abuse no matter what arbitrary laws you put in place. The fact is only the individuals involved can know if abuse is occurring, if adult-child relationships could be out in the open then you would have a lot less chance of an abuser getting away with it.

As far as the break up scenario, why would it be any different than an adult break up? If one person tells another it's over, adult or child what does it matter? If the 'adult' in question will not leave, well there are already laws governing that behavior, and they are aimed at adults now.

It is not my intention to attack anyone especially you plain, but I think you have to look at the whole argument, there are no absolutes in anything, there are always exceptions and just because the anti’s will do their best to never allow adult-child relationships does not mean we have to let them define the battlefield or the language we use to fight them. Do we have a long uphill fight on our hands? Yes we do and to make matters worse for the most part we have one hand tied behind our backs and we’ve been blindfolded; but still, if it just from the shadows we must do what we can to win, even if the only place you can do that is in your own mind.