Hi.
I know your situation must be frustrating. You must feel as though you've come so far with your parents--after all, they seem to be accepting your lesbianism, but not far enough. If you've "just" told your parents, give them some time. Mentally making the transition from how they imagined your life would be to reality will take some time.
To reduce the "demonizing" effect, you might try introducing your girlfriend to your parents, if they haven't already met her. If they've already met, ask your girlfriend to spend more time getting to know your parents--that is, if she has the stomach to take their initial iciness. Sometimes getting to know the real person, rather than some image fueled by stereotypes or buried resentment can make parents more accepting of the people you date.
You might also want to have a frank talk about this with your parents, letting them know that this is about something essential to who you are and not about something evil that someone has "done to you," that if your first time hadn't been with this girlfriend it would have been with someone else. I hope you can make it work, but there is a possibility that your parents will never be able to get close to the woman who "turned you out." This will probably not be the last person you date, though; they might accept future girlfriends more easily.
One resource that might help you and your parents through this is PFLAG, which serves the family and friends of lesbian, gay and transgendered people. Start with their "Getting Support--Coming Out" section at pflag.org, which provides the answers to questions frequently asked by lesbian, gay and transgendered people themselves, as well as those asked by family and friends. Refer your parents to the site, if you think this will help them to cope a bit better with your situation. You might also want to check out some of PFLAG's support groups. The organization has over 500 chapters located in all 50 states, so there bound to be one near you.
Good luck.
