President Donald Trump continued his fusillade of tweets insulting billionaire Charles Koch after Koch critiqued Trump’s tariffs as “unfair” and “ridiculous.”

Charles Koch of Koch Brothers, who claims to be giving away millions of dollars to politicians even though I know very few who have seen this (?), now makes the ridiculous statement that what President Trump is doing is unfair to “foreign workers.” He is correct, AMERICA FIRST! — Donald J. Trump (@realDonaldTrump) August 2, 2018

Trump’s first attack on the libertarian brothers came Tuesday when he called them a “total joke” and dismissed the massive fundraising they’ve done for Republicans of all stripes over the years.

While talking to reporters on Sunday, Koch expanded on some of the displeasure with the Trump administration brought up during the donor meeting last weekend.

“This is ridiculous, we should just get rid of all barriers except on things that will hurt people,” Koch said of Trump’s trade policies, per an ABC report. “Yeah, it’s unfair. It’s unfair to their people,” Koch said of countries hurt by the tariffs.

He added that he has “no idea” if they will trigger a U.S. recession, saying that “it depends on the degree. If it’s severe enough, it could.”