Apparently you haven't read the constitution.
The constitution states that judges have the ability to INTERPRET the constitution and the constitutionality of the laws passed. That's why they have lifetime appointments so they don't have to play politics.
Oh and it's specifically states in the constitution that a judge can't be punished for his or her decision nor have their pay decreased during their term. For the constitution lover you say you are, you sure do have a lack of understanding of what's in it.
Worse, she's ignorant of its case law, as the Constitution exists only in the context of its case law.
Federal judges can't just pull an opinion out of thin air and claim it's a 'valid' ruling, they must base their opinions on the precedent that is Constitutional case law, explain why the cited case law is guiding precedent, and ensure the case law is applied consistently to future similar cases.
For example, with regard to the many Federal judges who have invalidated un-Constitutional state measures seeking to deny same-sex couples their equal protection rights concerning marriage, those rulings are predicated on settled and accepted 14th Amendment jurisprudence whereby when the states desire to deny citizens access to a given state's law, the prohibition must be rationally based, it must be justified by objective, documented evidence, it must pursue a proper legislative end, and it must not have the effect of disadvantaging a particular class of persons motivated solely by animus toward that particular class of persons (See, e.g.,
Romer v. Evans (1996)).
Judges are consequently bound by this jurisprudence, and when they invalidate state measures denying same-sex couples access to a state's marriage law, they do so in accordance with their oath to defend the Constitution and obey its case law, having nothing to do with 'judicial activism.'