Such language might be authoritarian or it might not. It depends on the context.
"We must leave now in order to make it to the movie on time."
"You should put some ointment on that rash if you want to alleviate the itching."
Contrast those sentences with:
"We must invade Iraq or face a nuclear mushroom cloud in Washington."
"You should put your hands on the steering wheel or I'll shoot you in the head."
In short, language — even innocuous, innocent-sounding language — can be authoritarian if backed by hierarchical power. And language — even forceful, harsh language — can be non-authoritarian if done in a supportive, mutual environment (think of consensual S&M).
