There are stupid people everywhere, unfortunately.
Also sadly except in unusual circumstances (e.g. they have a trust fund to live off), pre-calc teachers are not going to know much about mathematics.
In my opinion, college calculus is poorly named and instead should be named "Pre-Calc" and the real calculus course is then physics.
Most of those courses are not calculus, it's just advanced algebra, and we do those trying for success in them a disservice with the dishonesty.