Willfully blind. Try pondering this phrase: Disparate impact.
A law against bar mitzvahs has a disparate impact against Jews since ostensibly they're the only ones wishing to participate in a bar mitzvah. Laws against gay marriage have a disparate impact against gays since ostensibly they're the only ones who would wish to enter a gay marriage.
Just FYI, I'm not in favor of gay marriage. But I'm not about to intransigently cling to ridiculous sophistry to make my case against it. I think there are better arguments than speciously (and flippantly in my opinion) offering that gays can simply marry someone of the opposite sex.
That does nothing to lend you credibility. It only makes you look like a domineering curmudgeon.
.... Laws against gay marriage ....There are no laws against gay marriage
There are laws that define what a marriage is, and what rights and privileges are granted to a married couple. A marriage is a union between a man and a woman. If you don't want to have that, don't get married.
As I said, an analogous law concerning bah mitzvahs, if you want to construct such an analogy, would be a law that required bah mitzvahs to be performed for anyone, regardless of their religious beliefs, and a that required the privileges and benefits of bah mitzvahs to be conferred on anyone, not just on those who believe in the Jewish faith.