I agree with the concern about Rackspace pulling down sites, but I can't help but be pleased with their decision on this one.
Do not confuse having a right to express your views in an open manner to mean that you do so without being held accountable for those views. What it means is that others cannot stop you from expressing those views, with rare exceptions. It in no way means that others can choose not to do business with you.
1. If you're making reference to the First Amendment, Rackspace cannot offend that. They're a corporation, not a government.
2. Even if you're not, why should Rackspace be forced to host someone's content that violates their AUP (and that they probably find offensive themselves?) If you don't like it, don't purchase their services.