That's nice, but it's not the only or even the most basic meaning of the word:
http://www.m-w.com/dictionary/discriminate
1 a : to mark or perceive the distinguishing or peculiar features of b : DISTINGUISH, DIFFERENTIATE <discriminate hundreds of colors>
2 : to distinguish by discerning or exposing differences; especially : to distinguish from another like object
intransitive senses
1 a : to make a distinction <discriminate among historical sources> b : to use good judgment
2 : to make a difference in treatment or favor on a basis other than individual merit <discriminate in favor of your friends> <discriminate against a certain nationality>
Definitions 1 (transitive and intransitive) are the most basic meanings of the word, and neither has anything to do with unfairness.
It's rather easy and unambiguous to determine when the state is making a distinction between people, and thus discriminating. It's takes a lot more to determine whether that distinction is unfair, and we're not all going to agree on that. And even if unfair, such discrimination is not automatically unconstitutional either.