Its not just Mattis.
"Retired Adm. Mike Mullen, a former chairman of the Joint Chiefs of Staff under Presidents George W. Bush and Barack Obama, has rebuked President Donald Trump's threats to use the military on protesters, writing that "our fellow citizens are not the enemy, and must never become so."
"Even in the midst of the carnage we are witnessing, we must endeavor to see American cities and towns as our homes and our neighborhoods," Mullen wrote in an op-ed for The Atlantic published Tuesday. "They are not 'battle spaces' to be dominated, and must never become so."
https://www.google.com/amp/s/amp.cnn.com/cnn/2020/06/02/politics/mike-mullen-trump-church-photo-op/index.html
"Writing that Monday's events "sickened" him, he said: "I have to date been reticent to speak out on issues surrounding President Trump's leadership, but we are at an inflection point, and the events of the past few weeks have made it impossible to remain silent."
Mullen said the president "laid bare his disdain for the rights of peaceful protest in this country, gave succor to the leaders of other countries who take comfort in our domestic strife, and risked further politicizing the men and women of our armed forces."
"Retired Gen. Raymond A. Thomas, former head of US Special Operations Command, expressed shock at hearing the term "battlespace" used to describe US cities.
"The 'battle space' of America???" he wrote on Twitter this week. "Not what America needs to hear...ever, unless we are invaded by an adversary or experience a constitutional failure...ie a Civil War."
"Retired Navy Adm. James Stavridis, who served as the Supreme Allied Commander of NATO, said that while it is necessary to restore order, "it hurt" to watch authorities forcefully confront peaceful protesters in DC.
He called on current leaders to keep the military "above the fray of domestic politics," writing that "we cannot afford to have a future Lafayette Square end up looking like Tiananmen Square."
"Former Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey tweeted this week that "America is not a battleground. Our fellow citizens are not the enemy."
https://www.google.com/amp/s/www.businessinsider.com/former-military-leaders-slam-trumps-handling-of-protests-2020-6%3famp