Words have meanings, and legal word very precise and well understood meanings.
It is constitutional by DEFINITION. Sorry for stating facts, but it is the job of the Supreme Court to test the law, it tested it, and it passed. While you can claim it's not constitutional because of this and that, it does not make it true, nor does it invalidate the supreme court ruling.
As an example: I, for one, completely disagree with the SCOTUS on its 'Citizens United' ruling that allows big business and big money to bankroll candidates. However, calling it 'unconstitutional' would be incorrect by definition. I can, however, call it undemocratic as it unproportionally favors certain demographics over others.
Just because a ruling is constitutional, doesn't make it right, just like just because something is law or tradition, does not make it right.
"Lighthouses are more useful than churches."- Ben Franklin
"Religious bondage shackles and debilitates the mind and unfits it for every noble enterprise."- James Madison