See, e.g., Washington v. Davis, 426 U.S. 229, 239 (1976): "The central purpose of the Equal Protection Clause of the Fourteenth Amendment is the prevention of official conduct discriminating on the basis of race. It is also true that the Due Process Clause of the Fifth Amendment contains an equal protection component prohibiting the United States from invidiously discriminating between individuals or groups. Bolling v. Sharpe, 347 U. S. 497 (1954)."
There is no such express "clause" in the Amendment.
Of course, even without such an explicit clause, I agree that the requirements in the Amendment apply to the the federal government, and should protect all persons.
At least the people's legitimate rights, of which sodomy is not one.
As usual, they have the world turned on its head.
DOMA is meant to protect states from having to accept sodomy fake marriage, just because other states have in some way or another (mostly by judicial fiat) accepted such immoral nonsense.
So, as usual, the Left has everything exactly backwards. This is just one more example.