Late Show host Stephen Colbert railed against Fox News host Tucker Carlson on Wednesday, describing him as a “little racist” as left-wing activists pressure advertisers to boycott his show.

“Carlson’s already got a reputation for flirting with racism, but last week, he took it to a racy new level,” Colbert began, before playing a clip of Carlson discussing the impact of mass immigration on America by making it “poorer, dirtier, and more divided.”

“Now, if just listening to him say that makes you feel dirty and more divided, you’re not alone,” the CBS host quipped. “Tucker got a lot of heat for those remarks, but he’s nothing if not the little racist who could. And he came chuggin’ back up that hill on Monday with a new reason he doesn’t like immigrants: He just cares so darn much about the environment.”

He then played a clip of Carlson arguing that immigration is “hurting this country’s natural landscape.”

“Right, good point, because Americans never do that,” Colbert responded. “Have you seen the desert after Coachella? I don’t hear Tucker calling to deport a bunch of Forever 21-wearing white girls named Blake.”

Colbert’s attack comes as Carlson faces an advertising boycott campaign organized by left-wing activists, that has already pressured some companies to pull their ads from the program. Earlier this year, campaigners launched a similar campaign against Fox host Laura Ingraham over comments she made about anti-gun rights activist David Hogg.

However, Carlson has received the unequivocal backing of the network, with Fox informing Breitbart News earlier this week that they will “continue to stand by and work with our advertisers through these unfortunate and unnecessary distractions.”

Follow Ben Kew on Facebook, Twitter at @ben_kew, or email him at bkew@breitbart.com.