Here is a lovely Talmudic tale from Bava Metzia 84a about the importance of debate and the problem of "Yes" people.
R' Yochanan who was swimming in the river one day and a thief jumped in the water to attack him, but the rabbi responds "Your strength belongs to the Torah" and after some negotiation the rabbi agrees to marry the thief off to his very beautiful sister, if the thief Reish Lakish agrees to study Torah.
Years pass by and Reish Lakish becomes a great rabbi with whom R' Yochanan constantly discusses issues of the Torah. One day they were discussing the issue of when various knives, spears and pruning forks become able to be tamei (ritually impure)? During this discussion R' Yochanan mentioned that Reish Lakish should know because "a thief knows his tools" and Reish Lakish was offended and responded saying that R' Yochanan had not benefitted him, since he was a "rabbi" among thieves and now he was a "rabbi" among scholars. Lakish's ingratitude disheartened R' Yochanan and so Lakish became ill and eventually died.
At this point R' Yochanan grieves Lakish's death deeply and the other rabbis decide to help comfort him by sending to him someone else who can discuss and debate Torah with him. They send one of their best students. However, when this new student is with R' Yochanan, he constantly says, "I know a saying in the Mishnah and defends your position." This new person does not argue and debate with R' Yochanan. R' Yochanan says, "You are supposed to by like Reish Lakish? With Reish Lakish, whenever I said something he had twenty-four difficulties in regard to that point and I would have to come up with twenty-four solutions and as a result the subject became clear. However, when you simply agree with me, I learn nothing new and the subject does not become clearer." This caused R' Yochanan to grieve even more and he soon lost his sanity and died!