Dr. Ben Carson, who told reporters this week he’s putting together the necessary infrastructure for a presidential run, on Thursday tweeted his thanks to supporters who spoke up to defend him against his inclusion on the Southern Poverty Law Center’s “extremist watch list.”

As the Daily Caller’s Chuck Ross reports, Carson actually made the SPLC’s watch list last October because of his remarks defending traditional marriage, but his presence on the list didn’t draw much attention until Legal Insurrection flagged it this month.

Legal Insurrection’s William A. Jacobson notes that “landing on SPLC’s Extremist list can be politically deadly, and also deadly in the real sense.” Floyd Lee Corkins, who shot a guard at the Family Research Center headquarters in Washington, D.C. in 2012, had found the FRC on the SPLC’s list of hate groups.

The SPLC even issued an apology of sorts to Dr. Carson:

In October 2014, we posted an “Extremist File” of Dr. Ben Carson. This week, as we’ve come under intense criticism for doing so, we’ve reviewed our profile and have concluded that it did not meet our standards, so we have taken it down and apologize to Dr. Carson for having posted it.

In its reporting, Yahoo! News refers to the SPLC only as “a national watchdog group … that tracks hate activity.”