This idea is something I've had in mind for a long time, and I posted this write-up long before I started seeing a public service announcements on US television expressing sentiments such as "using drugs supports terrorism". So don't down-vote me because I appear to echo this sentiment; in fact I don't. That is why I used words like "embrace" and "shun" instead of more absolute words. My point is that if you buy drugs from some looser on the corner, its like taking a piss in public -- true, it may do no lasting damage, but the people who live there shouldn't have to clean up after you, and they are the ones (besides you) who get hurt if you get caught with your stuff to speak. You certainly can't control international terrorism, but you can control whose hands the drugs pass through immediately before yours.

Of course, if you think beyond the middleman, drugs often do support terrorism...but no more so than oil, diamonds, or indeed, money itself.

Legalizing drugs would help incalculably; I imagine a future multi-national cocaine conglomerate would take a page from the DeBeers marketing department and start competing on the basis that their brand of coke is terror-free!

In the end, we all have to decide as a matter of conscience the extent of the moral implications of our economic behavior. Henry David Thoreau didn't pay a tax because he knew some of it would be used to finance the Mexican War. Did trade and investment in Apartheid-era South Africa prop up an evil system, or did it help that country transform into a democracy? I leave the question as an exercise for the performed while tending your own garden and hoping for a bountiful, trouble-free harvest.