Respect is an issue that comes up quite a bit in martial arts (I sometimes feel it comes up far too little in other areas of life). It's a tricky question at times, and to some extent truly is cultural. So how do we explain the concept, and its importance, to those who are lacking?
Those who seem to lack respect in the dojo typically have what I might deem a "Western" or "sport" mentality, which accords respect only to those who have earned it. In this case, simply wearing a higher belt, holding a higher rank, being older in years, or even being the person running the class, does not automatically qualify you for respect. Instead, those students demand that you demonstrate to them that you are their superior in technique, speed, knowledge, etc. This puts senior students and instructors in the position of having tests of strength or will with students, which varies from harmless to annoying to outright disruptive. It can break the flow of class, and makes people hard to train with. If you've ever done drills against someone who didn't do the assigned combination, tried to learn kata with someone who keeps pointing out how they did a move differently in their old dojo, or sparred against someone who ignored cautions, then you too have had your training disrupted by someone disrespectful.
The problem here is determining what, precisely, warrants respect. In dojo culture, in martial arts, it is usually a given that a higher rank, greater age and greater experience automatically qualify for respect, superficially at the very least. You bow, say "osu", and do as you're told, even if you might be thinking, "man, I could take you!" You are learning a fighting art, and in order to do so safely, you have to exercise caution, and trust in your seniors and do as they tell you. If you demand that they prove themselves bigger, stronger, faster than you, then the risk of injury greatly increases. People with this mentality usually don't treat weaker people very well, and frequently will intimidate or rough them up. They believe they're just demonstrating how great they are, when instead, they have totally missed the point.
So how can we help them change their perspective? One way is to present it as being a parallel to the idea of being innocent until proven guilty. Things might look bad for someone, maybe the evidence seems to point at them as guilty, but you do not assume guilt until all the facts are in. It's only fair. Similarly, that senior student might look slow, or weak, but they might really surprise you with their skill or experience. If you always take things at face value, you are in for some nasty shocks in your life. In martial arts, it is always safest to assume the other person could have some tricks up their sleeve that you can't handle -- it's usually true, too.
Taking it one step farther, suppose you are stronger, faster than the other person. Strength and speed are not everything. Suppose you also have better technique. Well, perhaps they've been doing this twice as long as you have, and although their body doesn't perform the way yours does, they've probably learned a few things along the way. Even suppose that you get the rare high rank black belt who is basically an ass: not as skilled, not as fast, and hasn't learned much along their journey so they say or do things that make you cringe. Well, that too is valuable, because you have just learned what not to do.
When in doubt, go for humility. It will get you a whole lot farther in life.