Sen. Orrin Hatch gave a feisty assessment of Obamacare supporters Thursday — an unexpected digression in the middle of an otherwise garden-variety speech on tax reform — calling them “the stupidest, dumbass people I’ve ever met.”

Speaking at the conservative American Enterprise Institute, the Utah Republican heralded the Tax Cuts and Jobs Act, passed in December, for eliminating the penalty for not having insurance under President Barack Obama’s signature health-care law.

“[Congress], finally, did away with the individual mandate tax that was established under that wonderful bill called Obamacare. Now, if you didn’t catch on, I was being very sarcastic,” Hatch said to laughs from the audience.

“That was the stupidest, dumbass bill that I’ve ever seen. Now some of you may have loved it. If you do, you are one of the stupidest, dumbass people I’ve ever met.”

Hatch’s biting language Thursday wasn’t entirely out of character. He chided Democrats early last year for acting “like idiots.” And in 2014, he called his opponents “straight old dumbass liberals.” But his remarks on the Affordable Care Act were perhaps the first public slip-up since he asked for more civility in politics eight months ago (“The first step,” the senator wrote in June, “is to speak responsibly”).

And Salt Lake City Mayor Jackie Biskupski, a Democrat, quickly called him out on it.

“This is disappointing,” she wrote on Twitter. “We can disagree on policy (and when it comes to the #ACA, we do) but name calling is never appropriate in public discourse.”

Hatch, who will retire at the end of this year, joked at the beginning of his address Thursday that he “hopefully” wouldn’t say anything that would make the event organizers regret naming him the keynote speaker. “But then again …,” he trailed off.

The seven-term senator spent 25 minutes mostly bragging about the tax reform package and praising companies who intend to reinvest in the American economy as a result. But, he said, “our predictions were pretty much ignored by the other side.”

Hatch said the new plan primarily benefits the middle class and businesses while he said repealing the individual mandate — which takes effect in 2019 — will help low-income individuals save money.

“This is one of the most regressive taxes in the tax code with lower-income families paying most of the freight,” he said. “By zeroing out the individual mandate tax, the new tax law took a major step forward in the ongoing effort to fully repeal and replace Obamacare.”