Why would you want an acquittal? What we want is a fair trial in a fair location. If the guy in question has broken the law then he should stand trial and be punished if found guilty. If he is unable to be sent to the US for trial, then he should be tried in the UK and if found guilty sent to prison in the UK.
From reading these articles, that is the crux of the matter. He doesn't want to go to the US because their prisons are a bit harsh, his mental health may indeed make it so that if he was sent to the US he would kill himself in which case he should most certainly be tried here, but wanting to acquit him?
There are plenty of people with the same mental health issues he has, and they don't run around breaking the law, if he is capable of distinguishing right from wrong and is able to make a choice between doing right and wrong, then he should answer for his crimes.