Originally Posted by Foxhunter
I agree with Rookie.
A horse like this can learn social skills if you have the right horse to train it.
Horses like her are invaluable and rare to find
I completely agree.
When I bought Woodstock back it was a real similar deal to the gelding you're talking about Joe. He was bought as a weanling, stalled until he was a little over 3, unhandled, aggressive rank mess. I fixed it on the human side of things and after he'd had the time out after gelding, my old sorrel mare took care of it on the horse side.
He went into the pasture with her, posturing like a stud and it took her about 30 seconds to put him in his place. She wouldn't take his crap, kept him out of the lean-to (which was pretty amusing, he hated the rain at first, it would be pouring she'd be right in the doorway giving him the grouchy mare stink eye while he pouted standing out in it) same with food, if he was respectful, he got to eat, if not she ran his butt off. He is now pastured with the herd and does well, he's low man on the totem pole.
On the other hand, like Cherie said, there are some that aren't fixable. I've met a few of those over the years too. They quickly find a new home.
Your best bet is to keep them separated or borrow a very set in her ways alpha mare (I also know folks that loan out their old molly mule for the same thing)