Saeth... you are not wrong in that individuals can be df or da for openly associated with a df or da person. I would question you as to what you mean by "force"? The company is telling and individual... if you want to be a member you have to shun... So an individual has to say "i want to be a member therefore I am making the choice to shun this person" If they CHOOSE to shun then they have made a value judgement for themselves that being a member is more important than contact with the person who is to be shunned.
Well, couldn't that argument be applied to anything? "No officer, I didn't extort money from him, he just chose to keep his kneecaps intact, instead of keeping the money he had in his safe."
If you are taking a negative action against a certain behavior then you are enforcing against the behavior.