The Brahmin barons are an important part of Senator Morales' political base, and he's up for reelection soon. The mutants at Jacobstown need to be driven off or provoked into an attack. The senator wants to be able to show he's taking a strong stance against the mutant presence, but there can't be any blood on our hands.
So, use the same tactics as you did against those squatters back in Oak Creek. Harass the hell out of the mutants, but don't kill them unless they attack first.