The illegal drug market will always exist, regardless of legalization. Why? Anything legalized will be regulated and taxed and many people will still find it easier to go around both.
Drugs arent special as you say, but they also arent the cause of the violence. Gangs will still be violent and kill each other. It will just be over something new. So yes, we might see a decrease in drug-related violence (im still not convinced of this though), but we will see an increase in violence related to something else being traded on the black market.
I also have a hard time seeing crack or meth being legalized when many people still sue the cigarette companies for giving them cancer. I think tort reform is also needed.
You're ignoring that legal things, even when taxed are cheaper and safer than illegal things. Legalizing something kills the black market for that something. The reason is simple and obvious, real markets tolerate real business and real business out competes illegal business because it doesn't have to markup the product to make up for the overhead of being illegal which is what makes up the majority of prices for drugs on the black market.
Drug dealers don't tolerate competition under threat of violence and charge as much as they can and have to make up for product lost to law enforcement, real business has to compete with other businesses on price driving the price down to reasonable levels and also delivers a better safer product.
This is a gross misunderstanding of the war on drugs that only takes into account the percentage of people who are in prison simply for drug charges. There is a lot more drug-related crime that would not exist if no one was imprisoned for drug crimes anymore so the statistic is simply useless.