This Anonymous KKK stuff is confusing but isn't this their website?
It seems to indicate an Anonymous source outed the GOP Senators but they are not denying that that they are legitimate:
Operation KKK, an Anonymous-led effort to shut down the Ku Klux Klan, has begun early. The hacktivist collective, who had promised to reveal the identities of up to 1,000 KKK members on the first anniversary of the Ferguson protests, has published dozens of phone numbers and email addresses belonging to members of the Ku Klux Klan.
TheAnonMessage ?@TheAnonMessages
Anonymous names US Senators Thom Tillis (R-N.C.), John Cornyn (R-Tx.), Dan Coats (R-In.) and Johnny Isakson (R-Ga.) as members of the KKK.
11:15 AM - 2 Nov 2015
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Joy Butler Are we going to get some supporting facts? I don't want any of them to be able to snake out of this.
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Anonymous @Joy Butler, that was a leak from an "anon" source. The real list of 1000 kkk members will be published on nov 5th by the original team who started operation kkk a year ago and who hacked kkk'S twitter accounts and revealed identities of some kkk members back then.
http://anonhq.com/opkkk-anonymous-unmasks-kkk-reveals-identities-of-prominent-members/
https://www.facebook.com/topic/Ku-Klux-Klan/108381552519797?source=whrt&position=8&trqid=6212744304454339570