why or why not? please explain

i just need reasons from both views on the subject for a paper and i need more than my own opinions.
my own view on it is, love is love regardless of sex
also people should be treated the same as everyone else, regardless of personal preferences and if they want to get married - let them. i dont understand why its such a big problem the way it is, cause their relationship status has nothing to do with you.
the only reason people don't allow this easily cause god supposedly said marriage is between a man and woman or what not and thats the only opposing point i have on why people don't believe gay should be allowed to legally married (wherever its still an issue)