Republican President Warren G. Harding hosted a Klan meeting in the White House!
In 1921 the KKK supposedly wasn't the terrorest organization it became in the 30's through the 60's. But that is still just an unblievable thing a president could possibly do.
I believe your implication is misleading. Harding went down to Birmingham, Alabama in 1923(?) and gave a speech(not at all well received) to a white audience on the importance and need for improving the rights of Blacks. That took guts, and is hardly the kind of thing a KKK member would do.