(CNN) -- Retired four-star Army Gen. Stanley McChrystal on Sunday criticized President Donald Trump for his approach to the presidency in a wide-ranging interview that saw the former top commander of the US and international forces in Afghanistan label Trump as dishonest and immoral.
"I don't think he tells the truth," McChrystal told ABC's Martha Raddatz on "This Week." When asked if he thought Trump was immoral, McChrystal responded: "I think he is."
"What I would ask every American to do is again, stand in front of that mirror and say, what are we about?," he continued. "Am I really willing to throw away or ignore some of the things that people do that are pretty unacceptable normally just because they accomplish certain other things that we might like. If we want to be governed by someone we wouldn't do a business deal with because they're their background is so shady, if we're willing to do that then that's in conflict with who I think we are."
"And so I think it's necessary in those times to take a stand," he said.
McChrystal also reacted to James Mattis' resignation from the Trump administration as Secretary of Defense earlier this month. Mattis wrote in his resignation letter that Trump had the right to a Defense Secretary whose views "better aligned" with the President's.
"If we have someone who is as selfless and as committed as Jim Mattis, resigns his position walking away from all the responsibility he feels for every service member in our forces and he does so in a public way like that, we ought to stop and say okay, why did he do it?" McChrystal said. "We ought to ask what kind of commander in chief he had that Jim Mattis that the good marine felt he had to walk away."
After Mattis' resignation, Trump tweeted that the two had an "interesting relationship" and that he gave Mattis "all the resources he never really had."
McChrystal resigned from his post under President Barack Obama in 2010 after he mocked key administration officials in a Rolling Stone article.
"I believe that it is the right decision for our national security," Obama said of McChrystal's exit. "The conduct represented in the recently published article does not meet the standard that should be set by a commanding general."
In November, McChrystal wrote in a column for CNN saying that "America is facing a leadership crisis."
"We've become increasingly obsessed with what national leader we're for or against," he said. "President Trump is just the most bombastic example of this phenomenon, which has been playing out for decades."