What Do You Do When a Total Heretic Says Correct Things?

I heard a friend ask that question recently, and I have since put some thought into organizing some longstanding ideas on the subject.

First, we should not be surprised when this happens.  Even a clock that doesn't run is right twice a day. More seriously, God's common grace brings about the refreshment of rain on the just and the unjust alike, and even a heretic will typically recognize that he is wet -- and he may say something insightful or beautiful about the event.  Sometimes, even the best among us fall into this mode of thinking in which we imagine that those who are against us are wrong headed and evil in every way. Of course, upon reflection, any remotely thoughtful person recognizes that this is really not the case.  Those holding, in my understanding, even the most pernicious views -- barring some form of insanity -- will share many thoughts in common with my own. 

Anyone who wishes not to be narrow will find the need to read and interact with views that differ from his own, and appreciation for God's gifts to others will cause us to realize that God has given insight to those with whom we disagree on various areas.  While I am reformed in my views, I recognize that there is considerable variation even if I were to restrict my reading to the historically reformed, and I also recognize value in the writings outside of my own stream of thought. I recenty wrote a post commending some thoughts of G.K. Chesterton.  Chesterton, a Catholic with whom I would disagree about much, also said much that I would consider worthwhile, and I could encourage others to read Chesterton's books.  I sing and love the hymns of Wesley, an Arminian, and read sermons by Spurgeon, a Baptist. These I find insightful and helpful, though there are issues about which I would have strong disagreement.

And, of course, I can benefit from and publicly cite disagreements with authors that I have strong antipathy for their views. This is true in both academic and popular discourse.

But what about someone who is notorious that says something I like?  My own approach is that it is counterproductive to rely on the support of someone who is thoroughly unsound, and if I need arguments or supporting material, I should take the time to find a more reliable source.  Hugh Hefner might have over the years said something I agreed with about sexual ethics -- maybe -- but I am not likely to quote him for positive support in Sunday's sermon. Similarly, the Watchtower Society or Pelagius, Joel Osteen, or Doug Wilson, or some other unreliable person may say something I like about God or worship or the Christian life, but I am unlikely to quote them. I really don't want to encourage anyone to listen to or read any of those sources, and those aware of their reputation may question my use of source material.  In the vast array of Christian literature, there are many others that can be looked to for illustrative or supportive material.

Of course, this recognizes a spectrum extending out from my own understanding.  There are some with whom I disagree, but I recognize that their views are within the broad stream of catholic Christianity.  Others fall outside that stream, and I regard them differently in terms of the way I would cite them. All of this requires discernment and care, but this largely explains my own approach to this question.