Because bigotry matters. It matters to who we are as a society. It matters to the people who are targeted by it.
I agree. But then I suppose it all depends on how you view the role of a forum like A2K. I see it as a conversation. If I don't want to have a conversation with a racist or a bigot, I walk away. I don't continue
the conversation just so I can express my moral condemnation of the other speaker.
You, evidently, view A2K differently. You may see it as a courtroom or a battlefield or town hall meeting. In those settings, I can see why you'd want to challenge racists rather than walk away. If, however, you also see it as a conversation, then all I can say is that I hope your interactions with people in real life are limited.
What is considered acceptable behavior in our culture does a lot to shape who we are as a society and as a country. A hundred years ago it was socially acceptable to refer to someone as "Nigger". We worked hard to change that, and this change is more than just words, it is a change in how we view people and what is right and wrong.
But we can show our disapproval by refusing to interact with people whose views we find reprehensible. Shunning, after all, is also a real-life tactic to shut down reprehensible viewpoints, and it works.
But there are also practical reasons. Consider growing up as a young Muslim and being faced with this type of hate speech. The posters in question are are claiming that Muslims are prone to rape and violence. You don't think this is harmful to individual Americans who must face this prejudice?
No doubt, but you assume that the only way to express disapproval of reprehensible viewpoints is to engage in protracted arguments with the people who express those viewpoints. I reject that assumption.
People of goodwill who want to live in a free fair and equal society must stand up against bigotry... or the system will fail to work.
Your problem is that you think there's only one way for people to stand up against bigotry -- your
way. I think you're wrong.