"In your world, people choose what sex to be attracted to. In your world, it is natural for a father to block all connections with his son because of a supposed decision that won't harm anyone at all. In your world, any father would be ashamed if its offspring was gay."
No people are brought up to be attracted to the opposite sex, it's the normal way of life like being brought up to not cause crime. Of course a father would cut off their son, a son is a fathers pride and joy, you want them to grow up to have a normal life, get married and have kids. Imagine the fathers embarrassment now if his friends find out his son was gay.
No parent wants their offspring to turn out gay.
Are you seriously comparing homosexuality to crime?! You're a goddamned despicable human being. Crime is an act that involves the deprivation or hurtful acts towards others. Homosexuality is an act between two CONSENTING adults. You might not like it, but some do, and they're not hurting you in any way, so live with it.
Oh my god! The father's pride has been tarnished in front of his friends! Quick, we must justify it by cutting off all communication with his flesh and blood and cause years of psychological distress, in order to save the father's pride! Are you really using this an an excuse to justify disownment? Answer me honestly, now...
In a way, I hope you have a son that turns out to be gay. Of couse, I would feel a lot of sympathy towards a kid with such a closed-minded parent, but sometimes the only way to get these ignorants to open their mind is to have something like this happen to them.