What if it was God's plan?

Several months ago, an argument rose between me and my friends about gay marriage, I was told that it is useless to try to convince a religious person that gay marriage is alright. However, if the people in the past did not even try, how did the society reach its equality between men and women, people of different statuses and different ethnics? Hopefully, by the end of this, you will think thoroughly about what is mentioned here.

Firstly, I have a question for you, what if my being gay was God's plan all along? What if Gay marriage was God's plan as well? What if a person who underwent a sex change is God's plan? And What if God wanted the person to learn to be able to embrace him/her true-self?
If you think that I'm being stupid to speak in God's behalf, then how about you? If you're the kind of person to speak about people's wrongdoing, when you're also sinning yourself, then you have no right at all, especially when this involves love and not bloodshed.

It's easily believed that passing your test or even failing is God's plan, so does death and natural disasters. However, when it comes to something that they themselves cannot experience or are told by a priest that it's a wrongdoing, then they won't think of it as a God's plan, rather a wrongdoing and it's against God.

Now, are you one to say that people who are in love are sinful when you're spreading hatred? If that is what you get out from a HOLY book, then I guess religion itself should be removed thoroughly. I am saying this, not because I am anti-religion or anything, but to show the negative interpretations people received from the bible.

Lastly, the passages and the teachings from each church/temple are different. In life, we get to learn that we cannot base our beliefs on one source of information alone, we have to gather all sources of information from different books, encyclopedia, articles and etc. A person should be able to visit each church/temple and see the differences in the teachings, not just that one church/temple where you can agree with every single thing the priest says. As human beings, we should see things from different perspectives, and not just the black and white.