Is looting and pillaging the norm?, Or is there room for some decency? Options

[ChronoGib]

I seem to have a different impression of what the SR world is like then my players and I was wondering how other groups run. I know I'm posing a no-right-answers question, but I'm curious how others play.

I've noticed my players have tendencies like;
1) Take anything not bolted down and assume the consequences can be dealt with. (Like taking comlinks for the sole purpose of selling them later.)
2) Be excessively violent. Example A, if they get attacked while in a gang's territory the players slaughter the gangers then chase down anyone trying to flee (then do #1 with the bodies, luckily organs count as bolted down). Example B, the guy's already hiding under his desk, but they decide to kick him in the head for no reason.
3) Disrespect Johnsons by being rude and acting like they call all the shots. (I'd have the Johnson just walk out if I wasn't trying to establish certain characters and events for the plot)

I'm a new GM and I own and have read the 4th edition core book, Mr. Johnson's Black Book and played a couple of sessions of SR 3 years ago. I have a distinctively different view of how things go in the SR universe and was wondering if I just have the wrong expectations. I was reading this thread and got the impression my players are just being grossly unprofessional. I obviously need to talk to my players, but I want to figure out what reasonable expectations are first.

Thanks to anyone who can spare some advice.