Whether it's a victimless crime or not depends on where they source the drugs. You could argue that aggressive law-enforcement is what causes reprisal violence, but that still wouldn't justify supporting it in another way.
Well, producing child pornography is a crime that is inherently victim-ful. (I do not include cartoon CP here) Producing drugs today happens to have victims because of social policies etc, but those aren't inherent to the act of producing the drug. There are victims in the production of certain modern day goods (like electronics, clothes, etc.) but that doesn't mean that manufacturing iPhones necessarily leads to exp…
Law enforcement knows drug consumers will continue to consume drugs and drug cartels will continue to be violent, so if they don't change their behavior, they are responsible for the violence they cause.
From another perspective, drug consumers know drug cartels will continue to be violent, and that drug enforcement agencies will continue to enforce. From their perspective, if drug consumers don't change their consumption patterns, they are at fault for the violence.
If none of the parties change their stance, everything stays the same. Consumers blame the government for drug crackdowns, the government blames consumers for consuming and supporting.
Everyone is at fault. The practical way to look at this is how do you effect change with the least amount of effort? Is it easier to create legislation that change the government stance on drugs, or is it easier to do a public opinion campaign to change opinions on drug consumption? Seeing as how drug addicts are rational about their drug use (aside from dopamine=good), it's probably easier to pass legislation.