Piper's Appreciation for Fundamentalism

In spite of fundamentalism's warnings about his ministry and teaching, John Piper thanks God for the fundamentalists:

What I want to say about Fundamentalism is that its great gift to the church is precisely the backbone to resist compromise and to make standing for truth and principle a means of love rather than an alternative to it. I am helped by the call for biblical separation, because almost no evangelicals even think about the doctrine.

Piper certainly knows fundamentalism since he grew up in Greenville, South Carolina and his father was on the board at Bob Jones University. I appreciate his willingness to see that even fundamentalism has something to contribute to our understanding of what it means to be a disciple of Jesus. But it is precisely the issues that fundamentalism uses to criticize Piper that demonstrate their inability (or unwillingness) to consider whether or not they have taken the doctrine of separation so far as to have fallen into legalism.

For example, Piper is criticized for offering "enthusiastic support for Daniel Fuller, who has publicly undermined the traditional understanding of the authority of Scripture." Piper points out that while he is unashamed in his admiration for Daniel Fuller, the two do have their disagreements, "so it would not be helpful to talk in terms of an unqualified 'endorsement.' " But for fundamentalists, once you say almost anything postive about another who has some belief that doesn't sit well with fundamentalists (like not being a dispensationalist), you are immediately thrown under the bus (a doctrine they refer to as "double separation"). Surely there must be some parameters within which we exercise the separation card.

I wonder if, since Piper has offered an "endorsement" of fundamentalism, will the fundamentalists who have chosen to separate from him now have to separate from themselves lest they also be declared guilty by association?