Here is the only argument needed:If you prefer marriage law as is, between one man and one woman, you aren't a homophobe or a bigot. They only say so, because they lack a good argument to redefine marriage to include two men or two women.
A man has the right to marry a woman, a woman should have that same right.
A woman has the right to marry a man, a man should have that same right.
There is no rational argument against gay marriage, your selfish whining that you don't want the law to change isn't a good argument.