Coming out to one’s parents can be fraught with emotional issues, denial, anger and, yes, even acceptance. I’m sorry to hear that your dad had such a negative reaction about your coming out. But you’ve taken the first big step and now you can choose to keep your sexual identity private or continue to share your reality with your father. This may mean taking the chance that he’ll “freak out”on you again but then again you will never have the chance to receive his acceptance if you both pretend that it does not exist. Maybe if you broach the subject a little more delicately this time and explain to him that your sexual identity is important to you but only one part of who you are. He might be afraid that you are no longer the person he thought he knew. Reassure him. But stick to your guns if this is important to you. Hopefully your father will come around with time and become supportive or at least acceptant. Right now things are “back to normal” but only on the surface. He hasn’t forgotten what you told him, he may be hoping that it’s just a phase or maybe he’s just not ready to accept your lesbianism.
As for the meetings…do you need your father’s approval to attend the meetings? Do you even have to tell him at this time what kind of group you will be attending? If you do and you feel you would greatly benefit from attending the group, then I would urge you to give it another try and see if you can get any further with your dad.