I agree with what has been said. People all have different sexual preferences, and certain ones, such as what you've described regarding your son, aren't necessarily indicative of one's preference in their partner's gender. I bet there are many hetero men who like to stimulate themselves via their ****. It all boils down to what feels good to that particular individual.

I also want to emphasize that homosexuality is perfectly fine and the reaction that his father has had is unhealthy to young man who is just discovering his own sexuality and preferences. I had a very religiously oppressive grandmother, who tried to drill unto me her values and that homosexuality was "evil" and "wrong". This caused a lot of emotional and sexuality based turmoil to which I struggled to find peace over until my early 20's.

I can understand where his father might be coming from, however, as the man he expected your son to grow up into might not necessarily be the one your son will be and excepting that is very difficult if one was raised in a certain light to only accept certain outcomes.

Anyways, rest assured that your son is just being curious and exploring newfound, hormone fueled feelings, and discussing with him his curiosities and how best to control them will benefit you both. I wish my own mother had discussed these things with me at least a bit further than shouting at me what I would do about "sex" during an argument we had over peer pressure. However, given her aforementioned mother's methods and values, I hadn't expected very much in this department.

Best of luck to you and your son both!