You have to attack the message, not the messenger.
If you disagree with what pathguy has to say, bring some arguments that contradict his opinion, and not arguments of a kind:
"his head is so big you cant fit in the same vehicle"
"has a really foul odor!"
Size of someones head and the way people smell have nothing to do with the arguments that they bring to discussion.
Pathguy brings very strong arguments against liver flush, like:
"> Real Gallstones are faceted polyhedra, like the ones in the picture on the links below"
"> Real Gallstones sink in water. (As an autopsy pathologist, I'm
> very familiar with this.) The "gallstones" you'll produce from
> this recipe will float, as the "alternative thinkers" themselves
> point out. (They claim that real Gallstones float, too. Liars.)"
There are other ways how to deal with arguments that pathguy brings forward, without insults and low kicks, like for example: