Long story short, my dad believes that I have corrupted morals for being gay and I'm not sure what argument I could use against it. What would you guys say if told you have no morals for loving who you love?
Uhm... What exactly about being gay is immoral? What about being gay influences you to do bad things? There is absolutely no connection between being gay and immoral. Some of the nicest people I've ever met are gay and there's nothing wrong with it, so I would ask him how his morals are better than yours when he is condemning you for being gay.
People think that gayness in particular is immoral because it flouts the natural establishment of male+female, which was initially put in place so humans could reproduce. Now that that's really not a problem anymore, we can do whatever with no reproductive consequence, but people still see it as destructive somehow. It's a weak and flawed argument to call homosexuality immoral, but is also vague and "from the gut" enough that people will stick to it anyway.
I would just say: My morals aren't corrupt, but your perceptions are... and it saddens me that you aren't able to see that right now.
I'd tell him that you love whoever you love, and it's not for him to decide. If he really won't listen to you, just tell him to take a cultural sensitivity class. Ask him what about being gay is so bad and why he's so opposed to it. Pick his brain. Get all his excuses for believing being gay is immoral, and then come back with your own arguments. He may get caught in his own words and realize that he really doesn't have any excuses for opposing your lifestyle. Really, I don't think there's any good argument against homosexuality. It's about love, and there's nothing wrong with love. It says in the Bible that anyone who knows love knows God because God is love, so by that token, a gay person who is in love knows God. It would probably help if I knew exactly in the Bible where it said that, but the argument still stands.
