The reason “deny” or “denial” or “deniers” is such a useful appellation to slap on people you disagree with is because of a phrase that entered the lexicon to describe an actually deranged point of view: Holocaust denial. Every time a variation on “deny” is used in such willy nilly fashion, the user is implicitly linking the target of your words to those who reject that the Holocaust happened.** Leave aside the damage this does to the ability to have a rational debate on the issues: that’s just a gross misappropriation of a humanitarian tragedy to score cheap political points.
Now look: there are any number of reasonable debates to be had over this practice [Planned Parenthood selling "baby parts"]. Maybe the practice of selling dismembered-fetus organs actually saves lives! Maybe it is not only legal but also moral! Supporters of Planned Parenthood could try to convince us of these things. Instead, however, they say things like: [HOAX!]Ad hominen logical fallacy. Don't deal with the facts, don't deal with the argument, shriek "Denier!"
And he does not even deal with Catastrophic Anthropogenic Global Warming deniers.