Generally, somebody who has been a member for more than a couple of years would feel entitled to call someone who has been a member for 3 months a "noob". That said, unless a post seems particularly trollish or insulting of a long-time and well-established FReeper, it seems somewhat lacking in substance to question someone just based on the sign-on date.
Regarding your initial post with the “already posted here” comment, the thread that you linked had to do with states joining the lawsuit against the federal government which is quite a different matter from passing state laws prohibiting enforcement of the federal statute.