Yes, this is horrible and no, from a utilitarian perspective this does not make sense. You are basically argueing for chemical castration. This is exactly the kind of medicalization attitude which is very dangerous. The correct way isn't pumping our youth full with hormones or other chemicals, but giving them sufficient therapy and care and by ensuring that their environment in jail accommodates for a safe return into society, instead of turning juvinele youth into professional criminals and joining prison gangs.
Just to be abundantly clear I think this is a terrible idea. But I'd like to see it dispassionately debated on its merits. One could make the argument that "sufficient therapy" is reminiscent of the "no true Scotsman" fallacy. I do not know of any methods that can reliably work with the most violent of offenders. Chemical castration is evil, but so is life imprisonment. Which is lesser? Does it matter if it were a choice?
Why would you favor chemical alterations instead of simply changing the laws so this large portion of the population doesn't feel ostracized?
I'm not sure the current trend of labeling a lot of things as deficiencies is healthy for society. ADD, ODD, all that stuff should not be "treated" as much as it is today. Society should shape around how people are and not vice-versa.
We're at a point where having testosterone is starting to be seen as a problem which could be remediated by chemical castration for some people, and this is truly disturbing.