Firstly let me say that there are all kinds of paraphilias out there and if you can imagine one then it probably exists. People who are drawn to removing perfectly healthy limbs are a tiny fraction of the population and much smaller than the percentage of trans people in the world. Hence if we are between 0.6 and 1% of the population then these people represent an infinitesimally smaller percentage which in of itself should be revealing.
Secondly and more importantly, cross gender identities must exist because the imperfect biological process which forms a human being necessarily contains anomalies and variations. We do not even understand what makes us think we belong to a particular gender. So while we know we are either born with a penis or a vagina we do not comprehend the process of how that translates into a mental picture for each individual.
Thirdly, not all transgender people who have experienced cross gender arousal wind up having surgery which would distance them from the BIID people who are single minded in their drive for surgical intervention.
For the sexual paraphilia argument to work you must also be able to prove that they begin well before puberty since most trans people trace their cross gender feelings to their early life. While I have no problem with this possibility, it is a tall order to do so conclusively. But even if I were to concede that Blanchard was correct (and I am not), it would make little difference as long as the end result was a happy and well adjusted individual and, since the vast majority of trans people fit this category once they are treated, any surgical intervention would have been worthwhile. The same cannot be said for severing a healthy limb which will leave you in a considerably less favourable state than before. Yes, I know I am dealing in semantics here.
It is clear that the aim of AGP wasn’t to provide solace to trans people but instead to stigmatize and interviews with Blanchard have clearly shown this. But in the end AGP has not been successful and transgender people are, for the most part, getting the help and respect they need. Gender dysphoria impacts both sexes regardless of sexual orientation and we could indeed argue that all are universally related. But if they are not, then we could also say that apparent similarities between different conditions labeled as a paraphilia is also skin deep and, when we dig below the surface we could find sufficient differences to be able to state that they are not linked.
The bottom line here is that we do not have enough evidence to conclude anything so we should stick with the happiness of the transgender individual as our main and most important barometer.