I don’t think you’re understanding this correctly. The headline is incorrect - this rule change does not allow aliens to purchase firearms in a state in which they do not reside. All this rule change does is eliminate the requirement that aliens live in a state for 90 days before they are considered to have “resided” there. That is a rule that has never applied to citizens.
This rule change does not grant aliens more rights than citizens, merely the same rights. We can debate whether even that is appropriate, but the “more rights” argument is inapplicable here.
Thanks for the clarification.