Gay Marriage, whats the big deal?

Im a moderate I dont have much in common with the right and I hate the Far Left with a passion however it seems the right hates the idea of gay marriage whether its due to the defenition, personal phobias or religious beleif. The Left Seems to love the idea due to equal rights for all. This is the one view i guess i leaned alittle to the left on but my view on it is, Im Straight, I won't be marrying another man, It doesnt effect my life in the slightest bit whether theyre married or not. If you beleive theyre going to go to hell fine thats your beleif and your right but they don't and even if they do they just want to be happy now. If you have a phobia of gay people then simply dont associate with them, they dont force themselves on people. At the end of the day due to our personal beleifs we make their lives harder and in alot of aspects more depressing due to the fact we push our beleifs on what they should be able to do. They dont have any effect on our lives or make our lives harder. So In the end my question is Why are alot of people against gay marriage, it doesnt effect us in anyway, why do we insist on making their lives depressing and harder due to our beleifs when they don't do the same to us? Gays are just as nice of people as straights if not nicer in alot of cases to be brutally honest.