Actually I agree with d_b for the most part. By not having to declare yourself as something, you completely remove the labelling of it. If you say "I'm gay", you're immediately stamped with all the associations that come with the word 'gay', no matter how truthful those associations may or may not be.
To this day my second regret in life is coming out how I did, by saying "I'm bi." For two reasons:
The first is that it would've been far more progressive (and fun for me :D) to just turn up with a boyfriend and be all "Oh yeah this is my partner" and let everyone else decide. And then later be all "this is my girlfriend" and REALLY confuse them :D
The second reason is that I don't really think of myself as bisexual, so to speak. To me, I like people. Gender doesn't matter - If I enjoy spending time with someone, that's all I need. But it's easier to say "I like both" than to say "my tastes transcend mere physical gender and social norms and operate on a personal, emotional connection." Ya dig?
HOWtotheEVER. In the case of presented to us, "Religious Parents versus Homo Offspring", I think it's important to come out in the classic sense.
The reason is that whilst confusing enough for the young gaybian, it can oft times be just as confusing for the parents, particularly in situations such as this. It helps to be told clearly and certainly; "this is who I am, I'm aware you may not like it, but it's a part of me. It always has been and I am still the same person".
It's an easier adaptation for 'risky' parents, and in this scenario I'm sure will make the transition easier for them.
It also has the added benefit of helping to debunk any negative stereotypes they may believe in, and help ensure them that is isn't a phase.
So in short, there's no super magical special trick, there's no use gauging their feelings towards homosexuality, and there's nobody else who can make the decision for him - The best way is the blunt and honest way.