I wonder if any of that has to be said at all? What if a lecturer did not set this prejudice upfront at all? However helpful emotions are in the learning proces

I wonder if any of that has to be said at all? What if a lecturer did not set this prejudice upfront at all? However helpful emotions are in the learning process, saying "this is tricky" or "this is easy" is not going to help. Instead, play on other emotions. Explain the theory, show real life examples, simple tricks, stuff like that, surprise them. But don't say "this is hard" or "this is easy". Let them decide.