When is the "knockout game" a federal crime?

Apparently only when the victim is black, and the suspected perp is white.

“Suspected crimes of this nature will simply not be tolerated,” said Kenneth Magidson, the U.S. attorney for the southern district of Texas. “Evidence of hate crimes will be vigorously investigated and prosecuted with the assistance of all our partners to the fullest extent of the law.”

How many black-on-white knockout attacks have federal authorities ignored?

Seems there's a double standard at Holder's DOJ.