Not the poet David Kirby; this guy is a journalist with no medical background who wrote “Evidence of Harm - Mercury in Vaccines and the Autism Epidemic: A Medical Controversy” (“controversy” being a mistake for “manufactroversy”). He has since worked relatively tirelessly against vaccines. In later years he downplayed the absolutely unsupportable mercury link, although certainly not the purported vaccine-autism link. Naturally, he uses every fallacy in the book to uphold that argument; in particular, he seems to enjoy skewering strawmen (and who doesn't?) and moving goalposts.
The basic argument in the book is that since each side of the autism-mercury debate finds the other side blind to evidence, biased and entrenched, there must be scientific disagreement. Therefore vaccines are dangerous and thimerosal leads to autism. He conveniently misses the fact that science clearly favors the no-link side – or rather, he explains it away as a conspiracy, coming up with stories about pharmaceutical conspiracies wire-tapping their opponents and paying off governments. Among the more interesting attempts is his Osama bin Laden gambit. As a result, Kirby now has his own blog at Huffington post (i.e. where every non-rightwing-fundie-wingnut loon seems to end up), in company with other anti-vaxxers such as Jay Gordon and Janet Grilo and with the blessings of HuffPo’s wellness editor, the bizarre, newage woo-purveyor Patricia Fizgerald.
Kirby has worked closely with Robert Kennedy Jr (on this, among other things), but Kirby is generally somewhat subtler (and frankly more intelligent) than the other dolt. For instance, Kirby (together with the insidious executive vice-president of Autism Speaks, Peter Bell) works here to drum up the respectability of (not evidence behind) the idea that vaccines cause autism.
Diagnosis: Devious and ardent fallacy-monger and strawmanslayer, Kirby is a shameless threat to public health and has influence enough to be considered dangerous.