I forget who said it, but as long as the response isn't "I'm never going to talk to you again," there's usually room for acceptance with enough time and enough unwavering conviction.
My dad was kind of in the denial camp for quite a while. He kept trying to convince me that I wasn't really a girl, trying to convince me that the serious improvement in happiness and self-esteem wasn't from the hormones or transition, it was from my recent weight loss. He tried to convince me that what I was feeling was just fetishistic, and should not be followed through with in real life, since he apparently enjoys thoughts of being female as an occasional sexual fantasy. And when we had an actual face-to-face talk about it, he seemed really appalled at the thought that I was taking estrogen and testosterone-blockers.
Ultimately, I knew it was just because he was having a hard time accepting it, because he always seemed to take a great deal of pride in introducing me to people as "this is my boy!" And through my entire childhood he had always attempted (quite often unsuccessfully) to get me to like the things that he used to like as a kid.
But now, a year after my original coming-out, having now also come out publicly on Facebook, changing my gender marker and profile picture to a female one, and having completely unwavered in my conviction that what I was doing was right for me, he has come around on the matter. No, he still hasn't completely accepted it, but many of his friends from the community that he lives at have come on Facebook saying that he told them what's going on, and they wanted to offer their support. So he has actually reached the point where he seems to be okay with talking about it to other people at least, which means kind of a begrudging acceptance.
I don't know if I'll ever get full acceptance, but this is close enough.
At least my mom is behind me 100%. Hell, she's actually glad that I'm doing it, because of how much more open and communicative I am.
