Hijab.... cheating......bad speaking.

Hijaab.... cheating.... bad speaking.
let me define it, Hijaab is hiding your beauty from strange Men, Cheating is copying other peoples work and calling it yours, bad speaking -gheiba- is to speak intentialy bad about others behind their back to put them in a bad position.
What is the view of Islam about these three?? Hijab, some say it is a must, some say not, Cheating, is clear not allowed, the Prophet- Salla Allah aleih wa Sallam- said: "man Ghashana faleisa minna". About Gheiba, there Koran verses are clear, it is as if your are eating your brothers meat.
My point about this is that i find it strange how people put the most weight about Hijab, oh, that girl is not a good girl, she doesn't wear Hijab, it doesn't matter that she is a kind and honest girl who doesn't hurt others.
Ok, actually this topic is in my mind for a couple of years, one of my friends had this situation, while in secondary school, the wasn't wearing Hijab, one time a teacher, Ikhsaia Igtima3ia came to the class to talk about Hijab, they were saying how bad these girls are who doesn't wear hijab, they instead of sitting houres in front of the mirror preparing theier hair they should sit and study, some of the other -Hijab and Jubba wearing girls- were agreeing, yes these girls are not good girls, just because of theier looking. What made me wonder, is that at one of the final Exams these Hijab wearing girls were asking the one without Hijab for answers, i know that my friend doesn't cheat because she believes in the Hadieth, so who is here the right and who is the wrong?
Just because you are wearing your Hijab you think that everything else is allowed? you can talk about others, cheat as long as you seem in front of the people Muthajba? i am not talking here about those who believe in it and are trying to be good people, i am talking about those ones who do it just to look good in front of others but the inside is not clean. I think that it is more important to be clean from Inside than wearing your Hijab or shorten your trousers, at the university some of the ones who had short traousers and long bears were cheating too, is that right????
Don't miss understand me, i believe in Hijab too, i just believe that if you want to be a good Muslim you should first understand what Islam is really about, and not only choose the things that are convenient to you.