The teachers have no such discretion, unless they've decided they want a career change. Otherwise, NCLB and testing-based teacher assessments pretty much demand that the teachers waste all their time propping up those who failed to do the required viewing.
Teachers have methods available to them to prevent uncooperative students from impacting the learning of cooperative students. They can write letters to the parents, send the uncooperative students to the principal, set up parent-teacher conferences... Flipping the classroom doesn't change this dynamic.
