My experience has been that most players are considerate and non-confrontational. There are always the exceptions to everything but I rarely experience it.
On a crowded course, most of us only ask that the group in front of us keeps up with the group ahead of them. If a group gets out of position, it is their responsibility to do what is necessary to close the gap. Letting people play through is not the solution in most cases. If the group is slow, constantly letting others play though just disrupts the round for everyone. Pick up the pace or pick up your ball.
On a less crowded course, it makes more sense for a 4-some to step aside for a 2-some if the faster/smaller group catches the slower/larger group. Sometimes people consider allowing a group to play through as some sort of insult ("We are not THAT slow ... let those SOB's wait!!). I look at it as common courtesy and hope it is reciprocated some day when I am in the smaller group.
Finally, if you are taking beginners out, consider doing so later in the day and play 9 holes (18 holes is a looooong time for an inexperienced golfer). I typically play a scramble with the grandkids. We all hit from various tees and then take the best shot. It is fun to see the sour faces of the group behind us when they note the kids teeing it up. Then we take off with our scramble and no one can keep up.