Perhaps Sen. Tim Scott or Congresswoman Mia Love should respond to him. Then again, why bother?
Notice his carefully worded qualifier: "For a five-month period that ends this week, every single elected Republican in Congress was a white Christian." This would exclude Scott, who won in a special election to fill out DeMint's term; apparently, to Grayson, that did not count as being elected. Love was not yet in office. Also, Eric Cantor, a Jew, lost in a primary and then resigned from the House five months ago. That is why Grayson worded his statement as he did.
Furthermore, Grayson counts the Mormons in Congress as “Christian,” which they are not. As well as other pseudo-Christians.