“Now is not the time for us to succumb to racism and bigotry," he says in policy paper.
“This is a tepid effort,” the 2016 GOP presidential contender said.
"I know many Muslims who were just as angry and saddened as we were."
Likely Democratic caucus-goers think the former secretary of State is more electable.
Bush criticized Trump's claims about Sept. 11 and the treatment of a protester.
Sanders and O'Malley took part, taking questions from the progressive group.
Complaints were also filed to keep Marco Rubio and Ted Cruz off the ballot.
The Republican presidential candidate timed the surgery so he wouldn't miss any campaign events.
Trump is feuding with historians over Civil War history near one of his golf courses.
"Our lack of leadership is now creating chaos all over the world," Bush said.