I understand you are shocked, and it sounds like you have a surprisingly small amount of knowledge, let alone experience, around illegal drugs, so you are very confused. And some of the posts on this thread may not be helping.
There is no evidence here that he is addicted, though obviously he could be. Coke isn't physically addictive in the way that some other drugs are - however, obviously users can become emotionally dependant on it if they use it enough.
It can cause some people to be verbally aggressive, in rare cases physically aggressive, but from that point of view I would infinitely rather date a coke user than someone who drinks alcohol to any significant extent. Alcohol has the much more deleterious impact on behaviour in my experience.
Coke may well be very common among his circle if he works in a highly paid, high pressure job.
Don't panic. Talk to him and find out more. Do some research (not on here - there is a lot of panic on here about illegal drugs, while heavy drinking is on some threads almost saluted).
Your friend is scare-mongering in saying it's a "gateway to heroin", anymore than drink is, or any other substance. The majority of coke users do not eventually become smack-heads.
Good luck.