One word: cliche.
Ever so often people make judgements based on cliches. As an Italian living in England, I have to put up with my share of that. Most people think at Italians as Mario Bros clones, short tanned guys with a black mustache and a big nose. That's not too bad, even if I come from Milan and not the south of Italy, and I try to explain to people here that there are big difference of looks and culture in the different regions of Italy.
Colombia and drugs is as association that people do because they don't know anything about that country. If you ask them to name 3 cities they couldn't. The only thing they know is what they hear on TV. You mentioned the Schwarzenegger movie Commando, where one of the bad guys is Colombian general Diaz.
I guess one way to look at it is: what do you care about the judgements of people who don't know a thing about your country? Let them talk, no one would take them seriously anyway.
If you haven't been there, and met Colombian people, and got to know their culture, any judgement is plain worthless.