The UK, Portugal and Israel have used it only on consenting patients, intended as treatment of an inability to control sexual urges rather than as a punishment, though Poland and some parts of the US provide for its use even without consent. Unlike surgery, it isn't permanent, either - indeed, at least one form is actually used for contraception as well. I certainly don't think the (female) friend of mine who used it while deployed in the Army regarded as mutilation. In fact, chemically speaking it is the female contraceptive pill, in a longer-acting form.
I do dislike the notion of blurring lines between punishment and treatment - on the other hand, there is a sort of therapy programme near here for paedophiles intended to stop reoffending, and I believe complying with that can be a condition of sentence or a mitigating factor in sentencing. Is that wrong? Is taking medication to block the hormones involved any worse than having therapy to deal with the urges better?
It's not quite that simple - yes, the prosecution can stop you being convicted on a more serious charge than agreed, but they can't stop you getting a more serious sentence than they recommend. If you were facing murder charges in New York, for example, the sentence can be up to life without parole. Plead guilty to manslaughter instead, and the worst you could get is 25 years with parole after 8 1/3 - but your deal with the DA might also include them recommending that you get 15 year with parole possible after 5. The judge might ignore that recommendation and give a harsher sentence (or indeed a lighter one) - and of course either side can appeal, too - but you're still safe from anything more than 25, thanks to your plea bargain. Of course, your own lawyer would explain all of this to you before you formally accept the deal and enter the guilty plea. (England has slightly different rules: the judge can actually get involved to a limited extent, by indicating the sentence he'd be inclined to impose during the negotiation stage, as I detail on the plea bargaining thread here.)As for plea bargains, I accept what you say: the judge decides upon the sentence once a crime is proved. But isn't the prosecution then practising some kind of deception on the accused: offering a deal they can only ask for? No, wait. It's surely in the power of the prosecution to offer only sufficient evidence to convict on the lesser charge if they want to, especially in adversarial systems like America's or ours. That makes it perfectly possible for the prosecution to make sure the bargain is honoured.
Thir is sort of right - if I went vigilante and kidnapped Polanski from France and dumped him in the US, the fact he'd been kidnapped wouldn't enable him to escape again: he'd have to go and finish his trial and serve the resulting sentence. I would still have committed an offence under French law, though, and the French government could extradite me to face trial for it - it just wouldn't help Polanski. Nothing unusual about that: a bank robber captured because his getaway car is stolen while he's in robbing the bank is still caught, even though the car theft is illegal as well. It's only if the prosecuting authority has broken the court's rules that it can harm their case against you - illegally obtained evidence or a questionable confession can be excluded, for example.