Hate Speech to Mention the Bronx?

So U.S. Rep. Charles Bass was told after he dissed retiring Vermont socialist Bernie Sanders:

"Bernie Sanders and his Sandernistas can go back to taxi-driving in the Bronx of New York City where they came from," he said at a Republican event in Fairlee, Vt. The recorded comments have since spread far and wide via the Internet.

"This is a bigoted racial slur," Harold Judd, of Bow, wrote in a letter to the Concord Monitor. "Shame on Mr. Bass for his intolerant hate speech."

Source

The reasoning above is pretty convoluted but since Sanders is white and the Bronx is mostly black and Latino, it seems that it is regarded as an insult to say someone is black or Latino. That itself seems hate-speech to me!

Sanders DOES originally come from the Bronx so maybe it is a slur to call someone a taxi-driver! I was a taxi-driver myself once in my youth and I never felt it to be a slur to be known as one.

Or was the reference to the Sandanistas the problem? From what I know of Bernie Sanders, I would expect that he DID defend the Sandanistas when they were ascendant in Nicaragua in the 1980s.