Tell your friend he's ignorant. And gay...
Has he even played it? I seriously doubt it. If he thinks it's 'Gay' simply because it has Disney Characters in it, then he is an ignorant gamer and person. If he is saying that it is 'Gay' because of the Music, then he deserves to be punched in the face. It's by Square Enix! Hello, they have like the best music in the gaming industry! And doesn't the label 'Made by Square Enix' mean ANYTHING to him?
If you want to dig deeper, Kingdom Hearts (all of them) go very deep, dealing with themes of life, death, light, dark, destiny etc. And the cosmology behind the Kingdom Hearts Universe is also deep and very well thought out.
There was a comic I found on the web that beautifully high-lighted this fact.
I'll try and find it and then I'll edit it in.