People who resort to dealing drugs tend to be scum. It's not like such people are going to become upstanding citizens with legitimate business concerns if drugs were made legal; they are most likely going to go on the other criminal endeavors. If they were capable of doing something else, they would have done it in the first place.
I'm always puzzled by this attitude. Though I don't have stats, my guess is that most people who 'deal' drugs are people who have a little bit of extra pot and sell it to friends. Obviously the big wholesalers aren't like that, and there are people that make a lot of money, and there's coke and meth and heroine, etc. But by and large drug dealing is probably a lot like scalping an extra Super Bowl ticket; most of the people that do it are one-time amateurs and most of the volume is wholesaled by pros. Or maybe it's like ordering a pizza, as in one person buys it and the rest throw in a few bucks to cover the costs. That's still drug dealing and is criminal behavior according to our moronic war on drugs.
At least at elite colleges, many of the people who do this go on to good careers at investment banks, law firms, tech companies, etc. This has been going on for decades, with generations of people who would never be considered scum eventually running society, though they did 'deal' drugs when they were young. And they had plenty of other options.
It's worth remembering that Nixon created the modern war on drugs as part of his successful campaign to win white racist votes during the civil rights backlash. Scum, given that context, sounds mighty racist to me.