I think the real racist is Trump, rather than Khan.
Trump implied that Gonzalo Curiel (the federal judge presiding over a class action suit against the for-profit Trump University), could not fairly hear the case because of his Mexican heritage.
Trump's management company quoted different rental terms and conditions to black rental candidates than it did to white candidates back in 1973. Trump called those accusations “absolutely ridiculous” - and then settled the case out of court.
Three years later...it happened again.
Three times in a row on February 28th last year, Trump sidestepped opportunities to renounce white nationalist and former KKK leader David Duke, who’d told his radio audience that voting for any candidate other than Trump would be “treason to your heritage.”
He's a birther.
He encouraged the mob anger that resulted in the wrongful imprisonment of the Central Park Five.
The men’s convictions were overturned in 2002, after they’d already spent years in prison, when DNA evidence showed they did not commit the crime. Today, their case is considered a cautionary tale about a politicized criminal justice process.
Trump, however, still thinks the men are guilty.
When two brothers were arrested in Boston in August 2015 for beating up a homeless Latino man (citing Trump’s anti-immigrant message when explaining why they did it), Trump did not even bother to distance himself from them.
Instead, he suggested that the men were "well-intentioned and had simply gotten carried away".