"If you don't fight like hell, you're not going to have a country anymore."
That could be interpreted as a figurative suggestion, which it probably was, and there's no way to prove it wasn't. Level-headed people can look at the phrase "fight like hell" to mean a lot of things, and it's often used in a non-violent context, like a courtroom, or any other number of places.
But there are a significant number of Trump supporters who are not level-headed -- the uneducated, shit-howdy redneck subset. And that phrase could only mean one thing to them. Therein lies the rub.