Being an "easy target" is exactly how Trump has beat out his opposition and fueled the ever-growing criticism against the left. He is a big believer in the phrase, "all publicity is good publicity". I'm not completely sold on that idea in principle, but he knows how to counter-conduct the media. The very fact that he's said one taboo thing after another over and over while still surviving on the political front serves as its own meme on the true effectiveness of criticism: it only works if you profess to an accommodation of its premise.
If Trump had operated upon the mentality that he should police his words for the sake of finesse and moderation--as you would suggest he do--all of the flack being thrown his way would still be centered around the "Muslim-ban". But, to everyone's surprise, it's become a peripheral critique against his character that's shouldered by the people who still support him--and have always supported him. As such, the media is forced to shift focus constantly in hopes of finding a fulcrum.
To that end, if the media hadn't focused on this quote as a means of distracting from Hillary, they just would have found something else--however minor--to use against him. This way however, he's actually highlighted an issue that people will care about and not simply brush aside as mere news cycle histrionics.
