A person can argue anything they please. Not all arguments have substance.
For instance, if I argued that the sun revolves around the earth, you could easily say my argument is self evidently false.
If I argued that KevinK created himself, that would be a merit-less argument.
If I argued that the universe just happened of it’s own volition, that would be a merit-less argument.
Likewise, if someone argues that homosexual acts are ordered to the same ends as heterosexual acts, the argument is self evidently without merit. Homosexuality is not ordered to the same ends.
A person can make any assertion they wish. But assertions don’t make reality.