I agree that physical violence is unacceptable beyond toddlerhood - but I would think that a child psychologist would be taking a sledgehammer to crack the proverbial nut-shell!!
If pushed, pretty much all of us (adults and children alike) would probably be of interest to a psychologist, but on the whole we get along fine without them. Once you've involved school/psychologists, you may find yourself on a road that you really don't want to be on, with a child who is in fact well within the boundaries of "normality".
I would persist with your own strategies first!
FWIW, my son isn't a "typical" boy either - he hates anything to do with football/superheroes/weapons/sport generally, and is obsessed with cathedrals, writing music, reading, and textile mills. But he still struggles to deal with his feelings when things don't go his way. It may partly be genetic (my DH isn't exactly patient), and I just see it as a very long slog, and lots of counting backwards from 20 (10 isn't enough!!)
And, Lizinthesticks: why is it "crap" to say "I do think that boys tend to be violent, and that there's no point denying it or making them feel bad about having those feelings"
Does that mean you would deny that some boys are made that way, and/or that they should be made to feel bad about something that's essential to their biology? Do you really believe that boys and girls are just the same? (Do you read the Guardian?)