I'm to say here must sound like the stubborn and naive advices of school teacher.
But I cannot give you better advice than the following because I experienced
it in direct way. And this naive explanation can be more reasonable than any
other astute and acute method.
How to get respect from juniors
My suggestion is easy but may be difficult to do it.
To have your juniors respect you, you should change yourself. You should be mightier than them and just. Consider who you respect. And consider why you respect them.
Usually speaking, the men whom juniors don't respect have some common features.
First, they just want to be respected but they don't help others much.
Second, they orders many things but they don't do themselves.
If you also have those features, it is impossible to have your juniors respect you. Change yourself. You shoud be able to show them you are better at taekwondo than them. When you teach, show them you practice 20 times if you tell them to practice 10 times. Everything hard. That increase your power. Never tell your juniors with no actions. Surpass most of your juniors in competition or sparing. And you try something helpful for them without words. Don't expect them to follow you, but show them it is helpful for them to follow you.
At first, if your juniors don't follow you at all, just practice for yourself alone, but hard everyday. Tell them to do something only for their sake, not for your sake. Help others and never remind them of your help. Don't expect them to change right away.
It will take at least 6 month or so. As time passes on, juniors will know that it is beneficial to do whatever you say. And they will respect you then.
It is impossible to have your juniors respect you without strongness and justice.
You may know all of these I've said. Then, you don't do what you know. It's because you want your benefit and not others'. Remember that you will not follow and respect your senior either if he want only his benefits and not better than you at taekwondo.
Change needs your effort and your pain. The pain comes from the oughtness to do what you don't want and to give up what you think you can get. That is the most difficult.
Only those who overcome that difficulty can be respected.