Yesterday there was a vote in the Senate on whether states should be required to honor the concealed-carry licenses issued by other states. Pro-gun Senators argued one way, pro gun-control Senators argued another way.
If there were a vote in the Senate on whether states should be required to honor the marriage licenses issued by other states, the positions of most would be reversed, as would the argument.
Principle is fine, but usually politicians use principle only to justify a position.
Humans are not consistent, nor should we expect politicians to be.