Overall, specific errors in reasoning should generally be highlighted instead of arguing that the other person is biased. One reason is because such an accusation is an ad hominem attack -- I think that such indirect methods of analyzing the rationality of an argument have an alarming potential to provoke mind-killing.
The more obvious and important reason is that citing a logical error/fallacy/bad interpretation of data is so much more reliable than trying to read emotional cues of whether someone is biased; this is especially true considering the lack of insight which we have into each other's mind.
I just watched Transcendent Man about the singularity and Ray Kurzweil in particular. It's well-made, full-length, and includes the most popular criticisms of Kurzweil: that his prediction timeframes are driven by his own hope for immortality, that the timescale of his other predictions are too optimistic, that his predictions about the social outcomes of revolutionary technology are naively optimistic, and so on. Ben Goertzel and others get much face time.
You can rent or buy it on iTunes.