But this underlines the problem in Romer v. Evans. In the hypothetical you pose, there is an amendment to the constitution that directly addresses the issue--the right to keep and bear firearms. So it is not judicial activism to apply the constitution as written. But in Romer, the case Judge Roberts helped in, there is not any constitutional provision setting up homosexuals as a specially favored class that you cannot discriminate against. The supremes in Romer invented that right and put it in the constitution. That is judicial activism.
Don't focus on the nature of the plaintiffs but rather the nature of the case. Otherwise, you are playing the Slime's game. The petition said "the legislature shall not pass any law" and in effect, was amending the constitutional clauses pertaining to the proper role of the legislature. That is what was wrong with the petition. If allowed to stand because it was deemed "good law" in that it suported marriage, then the next 50 petitions would be equally valid if they supported something vile. It is a technical argument but that is what strict constructionalism is all about. The decision didn't establish a favored class per se and you cannot say that was Roberts' intent by any stretch.