They're for gun rights within the scope of their interpretation of the constitution. It's starts out "We the people" and when you don't consider someone a person, you don't consider them to have those same rights.

You make the fatal flaw of thinking there's reasoning behind their beliefs. They make up reasons to justify their beliefs. These reasons are always narrow-in-scope and context-dependant, but are often presented as generalized statements. They will change their argument to suit their aims.

rules for thee and not for me

Before I noticed the source, I just thought, “Badass!” Then I had the same question as you.

Check out a prior example

https://en.m.wikipedia.org/wiki/Mulford_Act