Former high-ranking national security officials have endorsed Kamala Harris over Donald Trump, and one of them explained to MSNBC’s “Morning Joe” why the Republican nominee is a threat to the nation. Retired U.S. Navy admiral Steve Abbott, who served as deputy Homeland Security secretary under George W. Bush, was among the bipartisan group National Security Leaders for America, which consists of more than 700 former and retired senior military leaders and public servants who denounced the Republican nominee and recommended the election of Harris to succeed Joe Biden as the next president. “She…