Here is my analysis of those classmates of yours with extremely disrespectful behavior.
If I am loyal to you, would you see me as weak or cowardly? Of course you wouldn't. Nor would I see you as weak or cowardly if you are loyal to me. People only see loyalty as weak or cowardly if they're loyal to someone other than them, specifically, someone else that they don't like.
You are loyal to your teachers because you recognize and appreciate their wisdom and understand that they are trying to help you become a better person. Unfortunately, your classmates probably see those same teachers in the exact opposite way. At best, they're simplistic and shallow and see the wisdom and knowledge those teachers are trying to impart as unnecessary or irrelevant. At worst, they believe those teachers are only out to get them or make their lives miserable.
It's easy to see yourself as the hero if you sincerely believe you're surrounded by villains. And if you sincerely believe you're surrounded by villains, you'll want to deceive, disrespect, and defy those villains as often as possible. When you encounter others who will not join you in your so-called "heroic" quest to deceive, disrespect and defy those you call villains, you will call them chickens, chumps, cowards, doormats, pets, pushovers, robots, spineless, wimps or wussies. You will see them as phonies because you believe that deep down, they see all the adults around them as villains just like you do and they're just too afraid to stand up for themselves, when in reality, they see the adults in their lives in allies, and you're too blind to see that.
The best way to solve this problem would be if adults could find ways to prove that they're trying to do what's right for the kids they're in charge of, and that they care about the kids they're in charge of, without being seen as weak.