We generally don't ask students to 'think critically' about other established scientific laws either. By and large, we regard them as well-established by a large body of experimental work, to which undergraduate students don't have extensive access; and 'critical thinking' about such laws is not a useful pedagogical technique.
Thinking critically about Euclid's 5th postulate has given us the wonders of non-euclidean geometery.
I should hope we do. Critical thinking is essential to truly understanding them.