A Silly Question

Cass was schooling me on the equal protection clause recently and a random, silly question popped into my squirrelly brain.

First, the equal protection clause of the 14th Amendment:

No state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any state deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.

And now, the silly question:

Tangentially, if we apply the equal protection clause as it's written, doesn't it eliminate any limits on marriage or age or ability? Polygamy should certainly be allowed for every reason same-sex marriage is, but not only that, what about all the age discrimination?

Wouldn't any drinking age above 18 be unconstitutional under this clause? Clearly, we are depriving citizens of a privilege w/o due process of law. Could we even have a legal age of majority at all? Are 2-year-olds not citizens?

Just thinking out loud. Anyone know?

I should have said, "... as it's written and the courts have interpreted it" given that the courts have interpreted it to preclude state bans on same-sex marriage.

Yeah, I fully expect to get slapped, but hopefully it will be an educational slap.