If we ever get to a point in society where huge swaths of the population are unwilling to associate with Breitbart in any way, and legislators begin adding laws

If we ever get to a point in society where huge swaths of the population are unwilling to associate with Breitbart in any way, and legislators begin adding laws to the books about segregating businesses into categories of "have dealt with Breitbart" and "have not" and try to (unconstitutionally) apply different rules to each, then perhaps the courts and the public should take your claims seriously. But until then, you are describing a slippery slope that doesn't make me feel bad one whit. And to provide an example of this: "What if no one would rent a building to the American Nazi Party, or provide their offices and employees with internet access, or sell vehicles to their employees, or provide web hosting for them, because of the threat of boycotts against them for doing business with the American Nazi Party?" Or let's take it back 50 years: "What if no one would rent a building to the American Communist Party, or provide their offices and employees with internet access, or sell vehicles to their employees, or provide web hosting for them, because of the threat of boycotts against them for doing business with the American Communist Party?" Or substitute any extreme you like. The KKK, for example. What you're misunderstanding about free association is that every person - and every business - has the right to choose not to associate as well. Association is not compulsory, and neither is listening to speech. Bad actors like "actual Nazis" (I am not claiming Breitbart is such) do not have a constitutional right to do business with anyone they like. Free association doesn't mean the market must be blind to the participants involved.