Why is this father wrong in what he did? It was his, the father's, choice and I am assuming it was not easy for him.
It's complicated and in order to understand why it's wrong may require a mental freedom you do not have. It goes something like this:
A father that is not mentally damaged will not reject his son because he's a homosexual. Right off, you have to not be mentally damaged to know this. What I refer to here, as mental damage, is brainwashing.
Homosexuality is a naturally occurring phenomenon in the animal kingdom and among people. It is not a personal choice otherwise, any day at all you could go out and have sex with another man. But in your and my case, this will never happen or at least I know it won't in mine, because I know I can't decide to be a homosexual. Therefore, any teaching that homosexual is evil and an evil choice some people make is a lie, a brainwashing stupidity, a sick teaching.
But once this psychosis in implanted by religious dogma, with all the fear of hell and eternal damnation, and all the other horse shit religion uses to imprison people's minds, the person no longer has real choice.
So this is why it is sad. This father was perverted by religion as a child and imprisoned in a hell that causes him to reject his own flesh and blood against all biological imperatives that would otherwise make him love his own child. This poor man was fucked and being fucked he fucked his son, the very thing, of course, he himself believes is evil. But if you are a mental prisoner yourself, you won't be able to see this. Bigots are blind. They can't see their own bigotry.