Is it racist to only date black people?

Most people would say it isn't.

After all, look at all the all-Black and otherwise heritage-specific dating sites:

There is also a dating site for descendants of the Euro-culture zone. It's billed the "First All-Caucasian Dating Site". However, in the past, anti-racist groups have lobbied against "all-White" dating sites to have them shut down for discrimination. It will be interesting to see if the anti-racists let this one go.