I don’t see how these judges think they have the authority to srike down constitutional amendments??
The judges are out of control. In the affirmative action case, the federal appeals court ruled that the losers couldn’t afford to keep fighting something the people voted for, so the losers win.
In theory, there's nothing controversial about a federal judge striking down an amendment to a state constitution on the grounds that it violates the federal constitution; the U.S. Constitution says that federal law is "the supreme Law of the Land... any Thing in the Constitution or laws of any State to the Contrary notwithstanding." (Article VI, cl. 2).
What is, of course, controversial (to say the least) is the idea that banning gay marriage violates the U.S. Constitution; but that's a separate question than the one you asked.