Online Dating Discrimination?

The popular online dating service eHarmony was sued on Thursday for refusing to offer its services to gays, lesbians and bisexuals.

This strikes me as a silly lawsuit. What's wrong with a web site focusing on heterosexual dating? Surely there would be nothing wrong with a web site that only handled homosexual dating? Yes, it is discrimination, in a sense. But it does not seem like invidious discrimination. They think they have a special formula for heterosexual relationships, and they have no idea if it applies to gay relationships. If they were the only online dating service, perhaps I could see a problem. But they are not.