Rachel Maddow had a fiery response to the Koch brothers on Friday after receiving a letter from their lawyer.

The MSNBC host and the billionaire brothers clashed over Maddow’s report on Thursday about Florida’s “drug test the poor” law, which she said turned out to be an “expensive and embarrassing failure.” Maddow had said that an organization funded by groups affiliated with Charles and David Koch encouraged other states to adopt the legislation, despite its dismal results.

“Very frequently, when we cover the Koch brothers, we then hear from the Koch brothers’ lawyer,” Maddow said Friday. She told viewers that the lawyer sent a letter claiming that her report wasn’t true, and that it contained a statement declaring as much for Maddow to read.

“I’m not going to read their script,” the MSNBC host said during her show. “I’m not going to renounce my own reporting on this story, because the reporting on this story stands. It is true.”

Maddow added that she thought the Koch brothers were not used to being talked about in ways they did not like, by people who do not listen to their instructions.

“We will not stop reporting on the political actions and the consequences of the political actions of rich and powerful men, even if they send angry letters every time we do it,” Maddow said. “I will not read scripts provided to me by anyone else. I do not play requests.”