I don't think objectivity and salesmanship are mutually exclusive. I've seen teachers make learning material really interesting without having to sacrifice neutrality. They simply make me care about the material - good or bad.
OP seems to be encouraging teachers to "sell" the idea that the material they're teaching is important. If you don't make someone emotionally investing in learning the material, they'll forget 60% of it (on average). If you don't sell the material, it won't matter whether you were completely objective because students will forget most of what you taught them.
I agree that it's really important for teachers to encourage critical thinking. I just think that it's possible for teachers to encourage critical thinking while still selling the fact that you should care about the material.
OP seems to be encouraging teachers to "sell" the idea that the material they're teaching is important. If you don't make someone emotionally investing in learning the material, they'll forget 60% of it (on average). If you don't sell the material, it won't matter whether you were completely objective because students will forget most of what you taught them.
I agree that it's really important for teachers to encourage critical thinking. I just think that it's possible for teachers to encourage critical thinking while still selling the fact that you should care about the material.