Ya know. I have self identified as a libertarian in the past year mostly because it seems to agree with most of my thinking (notice the use of lower case "L").
I believe in free and open markets. I also believe in ethical behavior expectations. When these are combined, I suppose I would say that I do not encourage trading or doing business with producers/traders who employ unethical practices.
I am not even saying to exclude them from the marketplace per se, but that by saying we are a supporter of ethical practices, we should choose to not do business in any market with those who use unethical practices.
Take China for example. they are participating in free and open markets but they also condone or at least "unobserve" unethical working practices.
So, as a libertarian, i say don't "ban" them from the marketplace, but be a discriminating buyer and make the choice not to do business with folks who do those things we say we find unethical anymore.
In a free and open marketplace, there is nothing wrong with using one's own ideals and values to base business decisions on. Though there are some I have seen of late who under the guise of libertarianism and even anarchism who seem to making the argument that as long as the "price is right" then choosing to not do business with them based on ethics is "not" libertarian.
Being libertarian does not mean giving up ethics simply because they would affect your marketplace decisions.
That's like saying a someone who doesn't want to eat at McDonalds anymore because of their position on the whole minimum wage issue is somehow preventing McDonald's from doing business in the marketplace.
It might be an unreasonable or even illogical position they have, but as long as they are personally choosing to not do business there and not trying to shut Mickey D's down completely, there is no problem.
If enough people choose not to do business with an unethical market participant, then eventually the participant in question will either change it's practices to be more palatable to buyers or they will stop doing business because they have no one to trade with. That's life in a free and open marketplace.
Too many people have the incredibly wrong idea that libertarians are cold, heartless people who will put a dollar before people every time and that is simply untrue. Libertarians just want to do as they will and let others do their own thing as well.
Supporting trade partners who do not recognize individual liberty and suppress that is unappealing to libertarians in general. Of course, the same people who think of libertarians as cold and heartless are usually the same people who don't understand the difference between Capitalism and Corporatism.
The so called Libertarian dictators who want to tell others how libertarian they are or aren't based on their own views can go take a long walk off a short pier.