Not to be critical of someone I've never met, but it sounds like your dad has fallen victim to the flawed logic of every single anti-gay argument, anti-race, anti-anything another person would self-identify with.
Saying that they "just have to get over it" assumes that someone is in charge. In a broader and much more general context, the state approaches issues like marriage by asking "Should we legalized gay marriage?" instead of asking "Should gay marriage be legal?" The former includes 'we' and asks if that group should award some other group some privilege, therefore implying their authority on the matter.
I do agree that gays need to know how to handle discrimination. Maybe ignorance is a better word -- but not ignorance from the state or any other public institution. When your a member of a population under intense scrutiny from well-funded organizations who have incredible influence over how people think, it helps to have a thick skin.
On that note, I have a question: I was always taught to treat ignorance with kindness. I look at the more recent progress of the gay rights movement and don't see that kindness -- but it's working like a damn. If you could describe the ideal attitude of the gay rights movement going forward, what would it be? Kindness? Leading by example (i.e., fuck other people, I'm gay and I'm going to kick ass at life whether you like it or not)? Aggressiveness?
Personally, I think it would be amazing to see more gay families identify themselves and show the world that they are as strong as any other family. I look back at Stonewall, and it spurred the purpose of early gay pride parades -- to show people that sex (literally) with the same sex wasn't as bizarre as the public thought it was..... okay let's be honest -- they all know it's better. But now that notion is widely accepted enough that you can find your way to an amazing group of friends and hopefully family who see past that. What is the next most important thing that the gay community needs to show the world and how should they do it?