Literally did it on impulse without even thinking about it so I wouldn't chicken out, so I blurted it out.
I said "I'm bisexual. I like both men and women. No more anti-gay stuff from you, ok?".
He said, "oh go away, you don't know what you like". I think he'll understand eventually, he needs time to think.
EDIT: Showed him this thread.
I said: "Look, this is what I said to you, these are my online friends who are happy for me that I came out as bisexual."
He said: "Oh you don't know what you're talking about, you've never had sex with a man or a woman before, until then you'll never know."
And yeah, I am still holding on to my v-card at 26. I was insecure about that years ago in high school, but I'm honestly glad I've waited to mature first.
Proud of you comrade, that's awesome and so difficult. I'm sorry he didn't accept it right away. Hopefully he comes around 
Daddy.
Hi cosecantphi's dad. He's being open and honest with you. It's ok. That's a good thing! Ask your son some questions. He might not know everything. He might have a preference one way or the other, but he likes both so just respect him and their partner, whover that may be and still be a loving father to them both. It's ok 👍Now hug! 