I could, but why would I? Then I'd be among the very people I'm questioning, which would then question why I would need to question myself? You've not thought this through, have you?
> and that governments can pass arbitrary laws restricting sex
Yes, technically a democracy can pass whatever arbitrary laws it wants. Laws are not some magical force, just agreements people have made.
> Any law banning heterosexual sex would surely be struck down as unconstitutional.
Only if the people are willing to uphold the constitution. It too is not some magical force, just another agreement people have made.
> You, presumably, would be the lone voice in the wilderness insisting that the crazy law ought to be enforced on democratic grounds.
Under a democracy, the law is to the will of the people. Why do the people of the USA want sodomy laws in the first place?
You might be right that that the USA is well on its way to having a dictator who can become the lone voice who controls all, without concern for what the public wants, but that is not the current state of affairs and that individual most certainly won't be me.