Isn't it unfair to deny gay people happiness?
Yes. And no. As horrible as it is to say, life is not fair, and neither is God. But He is just.
Let's start with the "no" answer. Am I really saying that it's fair for straight people to date, kiss, get married, and have sex while gays and lesbians are forbidden to live out even one of their most innocent fantasies? Well...yeah.
Look at this way: God didn't say "you can have anything and everything you want no matter what you do". Never. God constantly promises us everything we desire, but He always adds a condition. We have to obey Him. Would your parents lend you money and let you stay out late no matter how much of the furniture you had destroyed that day? Sad but true, maybe, but God is not a doormat, and we have to give in order to get. We can't ever forget that He Is God. Pure and simple.
So, no, in a way it is not at all unfair for God to ask something of us in order for us to happy. However...
No. It isn't fair. How many times did I cry to God about this! "I've tried everything; I've done all I can! Why can't I have just one date, one kiss, one night?" But nothing changed, and I only got more miserable - even when God did give me the very things I had asked for! Nothing ever made things right until I realized the plain truth that life and God are not at all fair. The rich get richer, the devout are killed in poverty. My best friends get married and start families, and I can never even check a guy out. But, hey. That's life. It's a tough lesson to learn, but it's true. God is not fair. He is just.
In teacher's college, they told us that fairness is not treating every student alike. If one of them needs special help, is it fair to make them do the same things as the rest of the class? Should some people be allowed to wear glasses while others can see without them? You get the point. Fair is not something you will ever see -- and that's not necessarily bad.
This you can trust: that God knows what He's doing.
One of the most prevalent promises in the Bible is that we will be hated, persecuted, killed, and tortured. If you miss the last few there and never get to kiss another girl, you could say you got the better deal.
So stop worrying about what's fair. What's real can be so much better.