I think organizing a campaign to hit Colorado squarely in the tourism might make more of an impact on legislators than drawing the line at Coors. According to the Colorado Tourism Office it's an industry that employs about 200,000 people and brings in something in the realm of almost $10 billion, or put another way, $763 million in taxes (all data is circa 2007, from
here)
And what can Colorado provide for tourists that you can't get in neighboring gun-friendly states like WY, MT, and UT (except legal weed)? There may be some uniquely Colorado attractions, but anything that would draw me to the state off the top of my head (skiing, hiking, camping, hunting, climbing) can be done in neighboring states.
The downside, of course, is the same argument that was put forward about beer above -- if a tourism boycott really gained momentum, a lot of the people getting directly hit in the wallet wouldn't be the bad guys. Of course, the threat may be enough to make an impact, and writing to elected officials in Colorado and telling them your tourist dollars are better spent elsewhere due to their repudiation of the US Constitution is an act all of us non-Coloradans can engage in that might help our brethren stuck on what appears to be that sinking ship.