I simply don't understand the opposition to allowing gay marriage. How does it hurt you to allow same-sex marriage? Gay couples can already do almost everything a heterosexual couple can. They can hire a priest to conduct a wedding ceremony, declare their love and intent to live in monogamous relationship in front of their friends and family, change their names to share a surname, buy a house together, pool their finances, live together, add each other to their wills and life insurance policies, etc... Preventing them from getting married doesn't stop them from living a homosexual lifestyle, it just makes it more inconvenient for them because they can't use a marriage license to expedite the process.
That said, gay couples are denied at least one extremely important privilege, the right to visit their loved one in the hospital in those situations where only immediate family is allowed. This is an extremely important privilege for the gay couple and in my opinion, but it is such a small part of the overall marriage relationship that there is zero harm to traditional marriage in allowing it. There is no legitimate reason why same-sex marriage should not be allowed.
That said, I also disagree that denying same-sex marriage is a constitutional violation, based on sexual orientation, of the equal protection clause. Let's look at a couple comparisons:
Anti-Misogyny Laws
White man CAN marry white woman.
Black man CANNOT marry white woman.
Here, the white and black men are treated differently solely based on race. Thus, we have discrimination, and absent a legitimate reason, a violation of equal protection.
Anti-Same Sex Marriage Laws
Heterosexual man CAN marry woman.
Homosexual man CAN marry woman.
Heterosexual man CANNOT marry man.
Homosexual man CANNOT marry man.
Here, heterosexual and homosexual men are treated precisely the same, regardless of the difference in their sexual orientation. Thus, there is no discrimination and no violation.
Traditional Marriage Laws - A Second Look
Man CAN marry woman.
Woman CANNOT marry woman.
Here, man and woman are treated differently based solely on their gender. Thus, we do have discrimination, and absent a legitimate reason, a constitutional violation.