Donald Trump proposes to put fast food CEO Andy Puzder in charge of the Department of Labor, where he could bring his program of wage theft, automation, and sexism to workers nationwide. Unions and worker advocacy groups are not so enthusiastic about this proposal, and one of the ways they’ve tried to register their concern is by tweeting at Puzder. This has revealed something new, interesting, and pathetic about the wealthy, powerful, outspoken political nominee: he has incredibly thin skin. Puzder has been steadily blocking his critics on Twitter:

The Hardees and Carl’s Jr. CEO has blocked the Twitter accounts of at least five labor advocacy groups. This week, he even blocked one of the country’s most prominent union leaders, Mary Kay Henry of the 2-million member Service Employees International Union.

“Yes, the Twitter news is true. A sentence I can’t believe I’m writing,” an SEIU spokesperson told BuzzFeed News on Tuesday evening. The union is the second-largest in the country, and has been the main backer of the Fight For $15 movement to raise wages in the fast food industry.

As a veteran fast food leader opposed to wage hikes, Puzder’s beef with Henry and the SEIU seems clear. But he’s handing out the blocks more liberally than that. The cabinet nominee has also blocked the National Employment Law Project, the Economic Policy Institute, MoveOn.org, the Fight for $15, and the Leadership Conference on Civil and Human Rights — all organizations that advocate on behalf of workers, especially low-wage workers and workers of color.

These groups are sober, policy-focused, and polite. As NELP’s Judy Conti told Buzzfeed, “We’re not name-calling. There are no ad hominem attacks.” But Puzder apparently can’t even face being tweeted at about New York Times coverage of himself, at least if it’s a progressive think tank doing the tweeting.

Just think: a labor secretary who doesn’t want to hear from pro-worker groups.

Laura Clawson is a Daily Kos contributing editor since December 2006. Labor editor since 2011.