Respect

OK I was always taught to respect my elders, but I was also taught that respect it a two way street, that you have to give respect to get it. So why is it that when an adult disrespects a child, say like in a school teacher or staff member disrespects a student and you call them on it that they have 1001 excuses for why they aren't wrong, but you are?

OK for example I was always respectful, I came in did my work, didn't talk or cause any trouble, but one day I can remember clearly there was a roach in the classroom and everybody was freaking out so I got a dictionary and dropped it on it to kill it. Now the teacher who shall not be named snapped on me and told me to sit down because she told us not to leave out seats and I try to explain to her that I was only up to try and kill the roach, she said I was lying and I lifted up the dictionary to show her the roach. so at that point she yells at me and tells me that she didn't care and to go sit down, which was unnecessary and I said OK then I won't kill anymore roaches in this classroom and from that she somehow fines a reason to say "I know your mothers a bitch" and I'm like where did that come from?

So why is it that adults feel that they have god given right to be respected and then for no reason at all be disrespectful to kids and then wonder why kids are so disrespectful?

I mean you're supposed to be leading by example and when you do things like what I just explained you're telling us that its OK to be that way.