This is the problem - there is subset of individual policemen and entire departments that AREN'T courteous or reasonable. They start out hostile and alienating. The interaction also starts out at an a very unequal power level. When you are placed in this sort of situation, it is much harder (and much more important) to finesse it exactly right.
It can be done, such individuals and departments often aren't the sharpest pencils and with a bit of training and fore thought, you can work around them but it's harder. And also recall that not every alleged perp is all that sharp / sober or even interested in defusing the situation.
So play acting these types of confrontation can be extremely effective. Unfortunate, but effective.
'These are not the perps you are looking for