At best, this was a really stupid blunder by Scalise's advance team, and if any are still in his employ, he should fire them immediately to make clear he had no idea it was a Nazi/KKK Klub.
At worst, he is a closet Nazi and the truth will out. This incident will prompt an army of "investigative journalists" (muckrakers, if you prefer, as I do) to do some further digging to see if they can find a pattern.
In the meantime, prudence dictates not making any judgments or forming any conclusions.
I guess if you are willing to make the assumption that he didn't know who he was talking to ....
That's a pretty big leap.
We'll see how the GOP responds.
I've helped run two congressional campaigns. A candidate makes dozens of speeches to dozens of organizations every week. It is simply impossible for the candidate to know everything there is to know about those organizations. He relies entirely on his campaign staff not to walk him into something that will blow up on him.
So it is not a leap at all to understand how Scalise could have been entirely ignorant of the makeup of the group he was addressing.
Who has ever heard of EURO before today?
Every candidate has had his photo taken shaking hands with someone he later wishes didn't happen.
"Hey, boss, here's a donor. He wants his photo taken with you."
Ten years later, that donor turns out to be a serial killer.
Shit happens.
As for his campaign staff, though, there is no excuse at all for walking Scalise into a White Supremacist group.