Because he can take it.
Arians said Monday that Palmer doesn't respond to Arians' criticism of him. He simply gets ready for Wednesday's practice.
"That's why it's so easy for me to say it, because he don't give a s---," Arians said.
After Sunday's 16-13 come-from-behind overtime win over the Colts, Arians was asked how the Cardinals' offense can start playing better early in games. He responded that "the quarterback has to play better, simple."
Palmer declined to respond to Arians' comment, saying he's always trying to play better.
Of course Palmer minds the critical remarks, Arians said.
"Everybody does," Arians said. "But he's got enough self-confidence he can handle it."
Arians softened his tone on Palmer's performance over the weekend after watching the film. Palmer "played a whole lot better" than Arians had initially thought before breaking down his 332-yard outing, in which Palmer had one touchdown pass and one interception.
Palmer's teammates don't necessarily like seeing him get blamed for the offense's struggles.
"It's tough to see him take as much heat as he is, because it's not him. It's all of us," tight end Troy Niklas said. "We got to give him more time. We got to step up the running game better. There's a lot of things we're not doing to make him successful, so all of us really got to look at ourselves and take accountability and take some of the pressure off of him so he can do his job."
Arians tracked Palmer's slow start to the second play of the game, when he was sacked for a 7-yard loss.
"I think looking at the first-quarter offense, we take a quick five-step [drop], we can't get sacked," Arians said. "Those things have to stop. The first dropback of the game was a quick throw and Carson gets hit. That leads to him not playing as well as he can. We've got guys wide-open and he gets frustrated."
Arians added: "I'd get frustrated if I took a five-[step drop] and got sacked on the second play of the game. Yeah, I'd get real frustrated."