The person who really messed moz up is his mother.
Nobody messes anybody up. And if they do the line is, I believe, "They mess you up your mum AND dad." But maybe "mess up" is too strong a word. Your mum and dad just shape the way you're going to deal with people, I think.
Your mum loves you unconditionally, your dad constantly puts you down? Well maybe later you're going to love some people unconditionally, and put some other people down; the outsiders will see no objective reason for you to do so. Why would you praise a band line-up and ridicule this other guitarist? Because you're a proud father when your boys obey and a mean father when they don't? something like that.
(Interestingly, there's probably more of the young Morrissey in the rebel musicians that left than in those who stayed, but the old Morrissey would probably need someone to point that out.)
Questions a shrink might ask:
Why try to play people against each other? Are you hoping to relive your childhood, and be a spectator in a grown ups' fight?
Why try to provoke jealousy and need for recognition? Are you hoping people will act like kids competing for your affection?
Why try to play the victim? Are you hoping this will end the conflict and everyone will love you in the end?
And when none of this works to your satisfaction, why show shame and guilt? Are you hoping people will forgive, and blame your parents for everything?
Well, look above, it's working.
And why still want your daddy to love you when you've got so many mummies who love you no matter what? And why burden anyone else with that task?
You only have one dad. So you weren't good enough for him, and you're still torn between punishing him and telling the world you love him? Well, maybe your dad cares. But why would anyone who's not your dad care if you treat them this way? And why should people care if you don't love them? They'd have to have the same kind of issues as you. Well, a lot of people have issues, but you'd have to be really lucky.
I'm sure everyone realizes there are some people out there who are not professionally qualified to say that kind of stuff, but will say it anyway. And will still manage not to give a f. about 540 pages of npd answers to the Problem that is Morrissey. They probably wouldn't even read his psychiatrist's essay about him!
...Now, I wonder, is that what you meant by "emotional shutdown"?
Nailed it.
Oh and, does anyone else think Morrissey being raped by his Algebra teacher in the gym or something was his own little private fantasy and his own way to deal with his latent homosexuality and the, er, tension at home? No? Oh well, it's probably true then.