Neil Cavuto learned that the hard way this week after he lectured Rep. Michele Bachmann (R-MN) on House Speaker John Boehner's (R-OH) lawsuit against President Obama over his use of executive orders.
"Why not just fix things that are very, very wrong now rather than dragging someone to court over whether they overstepped their bounds? It just seems to me like an enormous waste of effort," Cavuto told Bachmann on Wednesday in an interview that devolved into a shouting match.
The negative feedback was swift and harsh. At the end of that day's broadcast, Cavuto said a "record number of emails" had arrived.
"They go pretty much like this," he said. "'Cavuto, you're a rude ass. If I were Michele Bachmann, I'd have a law against you.' Someone else said, 'Who do you think you are? [Bill] O'Reilly? You're an idiot. Quit blabbering, start thinking.'"
Cavuto apologized that the interview "got a little heated," but he maintained that his point was "sound."
Many viewers disagreed and the hate mail kept coming on Thursday.
"Even 24 hours later, a lot of you are more than a little hot and bothered," Cavuto said before offering another sample of the response from viewers.
One emailer said Cavuto was "extremely rude and overboard" in the interview. Another asked, "Off your meds again, huh Cavuto?"
One viewer even suggested that Democrats get preferential treatment on Fox.
"Boy, what an ass Neil was," the viewer wrote. "I will watch for a Dem to get grilled like that but won't hold my breath."
Others accused him of sexism, prompting Cavuto to play a clip from a heated interview he conducted last year with Rep. Earl Blumenauer (D-OR).
Cavuto ultimately defended his point that Bachmann and House Republicans are simply "posturing" and told viewers that his program is no echo chamber.
"Now some of you say you will never, ever watch me again for the way I treated a congresswoman who I otherwise very much respect," Cavuto said. "Well, then I respectfully bid you adieu because if you prefer only hearing the interviews that suit you than let me say good-bye to you now because the time's going to come again when I will probably offend you."
This post has been updated.