Is it justified that we have to respect teachers?
It is most likely in your own best interest to respect teachers so that you don't put them on edge and learn less than you could've from them. So I think it's in your best interest, yes, which I suppose is a type of justification.
If you considerable evidence to believe you aren't going to learn something from a teacher or would become less educated under a teacher, then respect would be less necessary as a teacher, but I believe you should still respect that teacher as a person if nothing else.
Isn't that too much.
I doubt it, respect is powerful, costs you nothing at least in a physical sense, and contributes to a global sense of well-being. If you are concerned you are not being respected, I don't think having less respect in general is the solution to that.
Does saying good morning ..changes anything ?
Good morning is an extension of your best wishes - a method of voicing support. Supporting your teacher should enable that teacher to teach better, unless that teacher is functioning under non-standard social protocols, and enable that teacher to better provide instruction.
I find it useless to respect people unless they earn it.
In that case, if you expect to be respected, you should be sure to take steps to earn respect yourself. Warning, this is going to get wordy:
The best way to earn to respect is to show respect, so if you want respect you have to respect those that you want to respect you that they might earn your own respect to fulfill the objectives of showing respect.
If they are still failing to earn your respect, then I'd exercise caution but still at least outwardly show signs of respect, because one of the partners in a mutually respectful relationships must be the first to show respect if showing respect is a pre-requisite for earning respect.
Maybe I'll come back and edit the wordiness on this down after I've had some time to break it down a bit, but for now I would just encourage you to try to treat all others with respect at all times as this should be aligned with your own best interests.
Okay I slept on it and think I may have a better wording here. I'll leave the old one in case that is easier for some people.
Four related conditions as follows.
X is showing respect to teachers.
Teachers are not showing respect to X.
X doesn't want to show respect to those that don't earn respect.
X believe respect is earned by showing respect.
So X either wants a license not to respect teachers, or the teachers to respect X.
What X can control:
X can show respect or not show respect.
Strategy 1: X does not show respect.
As X does not show respect, by X's own philosophy teacher's won't show respect. Therefore no respect is earned and no respect is shown.
It is possible teachers may take initiative to show respect. I'm not going to cover that possibility as we know X has already taken initiative in this example.
Strategy 2: X does show respect.
As X shows respect, X is worth of respect.
Case 1: If teachers operate under X's philosophy or similar they show respect to X. Mutual respect earned and shown.
Case 2: If teachers operate under another philosophy, they may not show respect to X. X has earned respect but does not receive it, teachers have not earned respect but do receive it.
Determining the optimal strategy then requires understanding pay-offs. Now, as the purpose of interacting with teachers is education, you could, for example, place a value of infinity on teachers receiving respect and a value of zero on teachers not receiving respect, as this should maximize educational potential. This would make strategy 2 optimal. If, however, education is not the aim, and minimizing cost is where respect confers a non-zero cost, then strategy 1 is optimal.
I don't know X's utility curve, but this is the game theory beyond my recommendation. I do assume a non-zero value on education and a zero cost on showing respect, because that is the curve I operate under and was how I determined my own actions when I was in a circumstance akin to X's, and that is why I will always recommend strategy 2 as optimal.