As I said elsewhere, good leaders survey the landscape and adjust their policies to best deal with changes on the ground.
This, Trump has done after Paris and San Bernardino, in regards to emerging domestic threats from ISIS. There were, as accompanies anything Trump says, cat-calls that he flip-flopped after he had criticized Pamela Geller several months ago for 'taunting' Muslims.
However, it appears now more Americans are agreeing with Trump's position, as reflected in his continued rise in the polls, especially in New Hampshire. I guess most people do not see this as a flip-flop but rather as a commonsense response to the danger presented to Americans from domestic terrorism.