Just because Trump says we need to stop the immigration of Muslims until such time as we can screen them more carefully, doesn't make him a white supremacist. Since some (if not a majority) of terrorists claim to be Muslim, it seems that Trumps cautious approach toward their immigration is reasonable.
As to the KKK supporting Trump, Trump can not be held accountable for what the KKK does or says. The KKK may have a somewhat distorted idea of who Trump is and for what he stands. It's about the same as saying the New Black Panthers support Barrack Obama. Obama is no more in control of what the New Black Panthers do than Trump is responsible for what the KKK does.