The first half of life's continuum tends to be viewed by those going through it as "up" (so to speak) and the second half as "down," with an inevitable midlife adjustment (crisis, in extreme cases) in between.<p>This may be half-addled philosophy, or it may be common sense, but I think it is fair to generalize about people in this sort of way and about how this might color their perceptions of age and youth. On the "youth" side of this, you do get a tendency to say, "the world is ours and we can conquer it" in every generation and this tends to lead to a brushing off of those who are not in the same position. Call it what you will and, if "arrogance" is too strong, pick your own word. It is not meant to come across as biased. Bias, I think, manifests itself not when we try to make observations about what we see as attributes of age or youth but rather when we treat the individuals we interact with according to type and not based on their individual worth.<p>Your point about young people often being unfairly discriminated against is well taken - all too true and essentially the flip side of the ageist coin. The lesson is to treat people fairly as individuals and not arbitrarily according to type.