Marriage Debacle

Now, with this post, I don't want to offend anyone but it's just something I struggle to understand; gay marriage. Before you shout 'homophobe!' this is NOT  what it sounds like. I really don't care if you are gay or straight, it really doesn't make a difference to me, everyone is the same regardless. The problem is, you see, gay people wanting to get married in a church or believing in God. I, myself do not believe in God and don't understand why, if God and/or the Bible condemns something or someone you are, you would believe it. There are many verses in the Bible which are homophobic. Here are some examples: 

Lev 18:22-23 "You shall not lie with a male as one lies with a female; it is an abomination".

 Lev 20:13 "If there is a man who lies with a male as those who lie with a woman, both of them have committed a detestable act; they shall surely be put to death."

Tim 1:9-10 "realizing the fact that (civil) law is not made for a righteous man, but for those who are lawless and rebellious, for the ungodly and sinners, for the unholy and profane, for those who kill their fathers or mothers, for murderers and immoral men and homosexuals and kidnappers and liars and perjurers"

This is just wrong in my eyes. How can the Bible be read and followed by millions when it makes comments like this. I do realise that the Bible teaches many good lessons such as the good Samaritan etc. 
Okay, I'm sorry if this has come across much too strongly and this is not how I am at all. I'm not a raving Atheist, it just confuses me that people still believe it when it condemns so much of what we see in our modern world (one crazy one is SHRIMP of all things).
I am genuinely sorry if I have offended anyone. Everyone has a right to believe in whatever they want, I am not trying to stop you and I am a big believer in equality, free speech and letting people believe in what they want (to be honest, I'm a bit of a lefty) but it just confuses me when people believe in something that completely goes against how they live their lives. It's like a pacifist being a violent terrorist, well not so severe but you get the gist.