1: Marriage is not a "right", it's a benefit society gives to a certain class of people.<quoted text>
Prove this is marriage's most basic essence.....what is your source for this 'fact'?
Otherwise state it clearly as your personal opinion/ wishful thinking.
2: Society gives the benefits of marriage to heterosexual couples because long experience shows that marriage of heterosexual couples carries a great number of benefits to society (for example: it civilizes men, making them more productive, and less foolhardy (and therefore less destructive)(see lowered car insurance rates for young males who marry)).
3: There is no evidence that homosexual marriage provides similar benefits to society.
4: Following the age old principle that intelligent agreements give benefits to both sides, it is therefore not in society's interest to give homosexual couples benefits that they haven't "earned".
Marriage is a contract. It's a contract between the people getting married. It's also a contract between, that couple. and the State. Valid contracts require that both sides get benefits. What is the benefit to society of giving a marriage contract to homosexual couples?
Until that's answered, there's no rational reason to give homosexual couples such a contract.