The purpose is expressed in the text. Nothing more; nothing less. Anything else is soothsaying and, thus, judges who are hell-bent on a result can just make it up. This is why the analysis in Romer (and Windsor) is so disingenuous. Kennedy is such a pussy. If you want to make homosexuals a protected category, fine. I disagree, but do it. But he knows they shouldn't be, so he creates this hand waving nonsense about "animus" and "purpose" and "hatred" that causes--nay, requires--him to conclude Bill Clinton is a bigot. And all the other liberal justices sign on--holding their noses, no doubt--because they want to present a unified front. It all is so disingenuous. The reasoning really is beneath the dignity of the Court.
In this context, Clinton was a bigot. He was also just politically inclined to make the decision based on advice from "political experts" around him.
I think Romer is one of the most interesting opinions and decisions in recent memory for the Court. I think it serves, and quite effectively, to add something to the rational basis test where there is something substantive attached to the "rational" portion. These are just judicially created tests in the first place, so I don't have any problem with tweaking them.
The Colorado amendment had no "rational basis" whatsoever:
"The amendment provided in part that neither the state nor any of its political subdivisions "shall enact, adopt or enforce any statute, regulation, ordinance or policy whereby homosexual, lesbian, or bisexual orientation, conduct, practices or relationships shall constitute or otherwise be the basis or entitle any person or class of persons to have or claim any minority status, quota preferences, protected status or claim of discrimination"
I suppose that this could have been struck down on the traditional rational basis test, as there is legitimately no rational basis that can even be read into this by the Court since the express purpose, admittedly by proponents, was discrimination against minorities of all kinds. I just don't have a problem with Kennedy adding to the decision by making it an overarching concept that a desire to harm a politically unpopular group, or an amendment/legislation solely aimed at stripping rights to a specific group, can never be "rational."
I'm not even entirely sure that it changed the test that much, it just added clarification on how far "rational" would extend. And if you look at the definition of the word, can it be "rational" to ensure that minority groups cannot use the political process to enact change?
Just curious, what would decision on Romer had been?