Brennan has repeatedly clashed with Trump on Twitter and on television, calling Trump's failure to denounce Russian interference in USA elections at a recent summit with Vladimir Putin "nothing short of treasonous". Without citing evidence or offering proof, he said Mueller had conflicts of interest of his own.
Brennan accused Trump of committing treason, which Tucker Carlson previously noted on Fox News is a capital offense.
Others who have earned their security clearance are also speaking out against the move.
Describing Trump's move as "inappropriate and deeply regrettable", they insisted "we have never before seen the approval or removal of security clearances used as a political tool, as was done in this case". Gates and Panetta also served as secretaries of defense.
"I would consider it an honor if you would revoke my security clearance as well, so I can add my name to the list of men and women who have spoken up against your presidency", McRaven wrote.
His comments came two days after he yanked the security clearance of former CIA Director John Brennan, saying he had to do "something" about the "rigged" federal probe of Russian election interference.
"There are few, if any, who have a more impressive record of service", Hayden said. And that's OK with me, because I like taking on voices like that. "I will not relent", Brennan tweeted after the announcement.
President Donald Trump brushed off criticism from retired Adm. William McRaven Friday on the lifting of security clearances of administration opponents.
Trump says the official, Bruce Ohr, is a "disgrace".
Webb argued that Brennan does not require a security clearance to go on television and wage a "partisan battle" against Trump and he is still empowered to say what he pleases. "For him to be in the Justice Department and doing what he did, that is a disgrace". A good leader sets the example for others to follow. He added, "So I think it's something that had to be done".
"Let him write his report", Trump said. "We did nothing. There's no collusion".
Trump repeated his belief the probe is a "rigged witch hunt. a sham. and these people led it", referring to Brennan and nine other past and current government security officials whose clearances he is considering revoking.
"This action is part of a broader effort by Mr. Trump to suppress freedom of speech & punish critics".