Why Hasn't John McCain Denounced Tony Zirkle?

From a blog at USA Today:

A congressional candidate appeared last Sunday at a birthday party for Adolf Hitler.

Yes, that Adolf Hitler. The one who brought us World War II and the Holocaust.

"I told (WNDU-TV in South Bend, Ind.) in the beginning that I'd
speak to any group that wanted me to speak," Tony Zirkle, a candidate
for the Republican nomination in Indiana's  2nd district...