In my opinion though, drug consumption isn't immoral. So dealing in drugs isn't a bad thing I think, its the violence associated with it that is considered immoral.

You would judge someone who dealt in alcohol during prohibition as a gangster or a thug because they had to use violence for business, but when it became legal again and the violence stopped whoever sold alchohol was just a regular guy running a business.

Consenting adults should be allowed to consume whatever drug they want as long as does not affect other people. Making drugs illegal does not stop someone buying drugs, if someone wanted to buy cocaine or heroin they could even though it is illegal. Making drugs illegal just causes violence.