In some ways, proactive opposition, of anything, almost takes the "moderate" out, don't you think?
I agree with previous posts and the examples of how often "moderate churches" really do speak out against Christian extremists. It more than likely happens most often within congregations, however, rather than in public or political protests. But again, that's why they are considered moderate. The media has a way of blowing even the most level-headed arguments way out of proportion. I think when churches (and church people) stand up to fight something publicly, such acts get attacked by the media more harshly than matters that leave faith and religion out. Perhaps this is one reason it seems moderate Christians are "passively protecting" extreme fundamentalists.
Perhaps in an effort not to seem like a completely differnt kind of whacko, those who are effectively opposing religious extremes which fall outside of the truth of the Bible are choosing to take a more mild mannered approach.