Something similar happened to me when I was much younger with my reasonably homophobic parents.
My mother was sobbing that it was just a phase, and that she'd speak to me about it again a few months later. Before those few months were up though, she found out I had a boyfriend. Living under my parents' roof, I was forbidden to see the 'boyfriend' again (really I was only meeting him to get away from a miserable home life, and was not actually that interested in a relationship or sex with him - more just someone to talk to). And my parents were very interrogative and possessive of me and my whereabouts - I was no longer trusted and being outside the house during non-school times was not on. And when I left school it was still the same and is the same when I go back home during holidays, Christmas etc. But it has become slightly less stifling over time. Needless to say I don't go back much.
About 5 years after the initial "just a phase" time, the subject of my gayness was finally brought up again - the news had sunk in by then, they were still angry at me my dad still mocked and threatened me but they certainly believed I was gay by that time.
You just need to give it time. You have just set the ball rolling by telling them. If you continue to argue you will set yourself against your parents and I know what religious parents' egos are like. They will NOT back down if they perceive a fight between you, and the bad-feeling might escalate. So let it lie, let the news seep through their god fearing veins through time. In the mean time, focus on acting exactly as everything was before you "came out" while NEVER bringing up the subject during this time UNLESS they bring it up. You could even try to brush it under the carpet if they try to bring it up as a result of them looking for a fight - don't engage in any fighting with them it will not help either of you. Your parents may be too unlearned about the world to realise this (mines are).
Presumably you still live with your parents as your home address and you depend on them for stuff (ehh maybe money for example) and they have power over you such as "in this house...", "we're feeding you..." etc???
----> So you may have to wait it out and not broach the subject again until you have released those dependences. ie finished college, got a job and moved into your own place. [surely an awesome day when it comes]. Also at that time, in the future, it would help to have emotional back up in the form of friends who would be there if it all goes badly?
But you've done well by preparing them now - and they probably have had ridiculous and wrong images of what a gay man is in their heads (think squealing bitches in high heels and naked people dancing in public that they've seen on TV). Do your own thing to passively demonstrate that they have nothing to fear in the fact you're gay, and that perhaps it's THEIR ideas that are wrong about gays. But don't ever explain this to them - it might cause fights again - use deeds not words. And concentrate on really getting on with your parents and having great love for them, getting along well with them and respecting them as your parents. Try to ignore the gay issue for a while and work on your relationships with them. All the time the gay thing will be solidifying in their minds as they get used to the idea and imagine you with a boyfriend one day, for example.
I love my parents BUT once I am financially independent I will lay down the law as far as my treatment is concerned and I will not ever again accept being treated as a 2nd class citizen in relation to my brothers (whose girlfriends have always been made extremely welcome in the house). We shall see what happens in our futures.