I think lobotomies should be revived. They'd be an excellent way to deal with sexual predators. Castration-lobotomy combo would do the trick reliably, while leaving most of the perps sufficiently functional to hold down simple jobs so their continued existence wouldn't be on the taxpayers' dime.
Contrary to popular opinion, a lobotomy does not generally have the effects it is portrayed to have in the movies. Other types of psychosurgery could be devised, doubtless, that would do what you want.