Ad Hominem _ directing an attack against the person making a statement rather than the statement itself.
“to the man”: ad hominem (subclass): “poisoning the well”
“Dr. Smith’s data on the cell is biased! Nobody could possibly believe anything this guy says! I mean, he’s a Creationist!”
Proponents of this fallacy attack the validity of a claim solely based on the beliefs or actions of the person or group making it. They can’t find fault with the argument so they sling mud at the source.