MS-13, for him, solves all kinds of rhetorical problems. So first of all, he wants to portray immigrants nationwide as being criminals. And that’s obviously empirically untrue. But also statistically, that’s wildly inaccurate. Crime in immigrant communities tends to be much lower. Immigrants tend to be much more law abiding than citizens.
It helps him shape the debate on DREAMers and recipients of DACA, the Deferred Action for Childhood Arrivals program, which is kind of a big congressional issue now ever since Trump canceled the program in September of 2017. He often mentions the two in the same sentence as a way of trying to sell wholesale draconian overhauls of border security measures and interior enforcement measures. MS-13 is useful for him there.