Carla: Professors at public universities should receive paid leaves of absence to allow them to engage in research.
Conclusion
(implied) Professors should not receive paid leaves of absence to allow them to engage in research
Evidence
Even if research does advance human knowledge and improves professors' teaching, why should we devote any of our limited resources to fund professors taking time off from teaching?
Evaluation
Calling it "taking time off from teaching" makes it sound like they're on vacation. If they're doing research that improves their teaching by keeping them up to date with developments in their field, then how is that even time off? When a teacher is prepping a lesson, is that "taking time off from teaching"? No, that's part of being a good teacher: training / preparation.
Goal
Look for answer that says that David is failing to consider that this research time isn't time off from teaching; it's basically a form of teacher training/prep so that they can be better teachers.