A tone troll is a serious-minded person who wants only to raise the level of discussion in the dire cesspits of the New Atheist web. Or, possibly, they're a pompous blowhard who, lacking such frivolous accoutrements as an actual argument, attempts to distract attention from said deficit by complaining that their opposition uses dirty words and ought, really, to have some strict nanny figure—possibly Mary Poppins—to wash out their mouths with soap.
Note that the presence of actual 'dirty words' in the traditional sense (notwithstanding that this is not uncommon on Pharyngula) isn't particularly necessary for the use of this gambit. It is also acceptable to complain your opposition is being shrill.
When people finally tell the tone troll to go away, it will sometimes accuse them of "kafkatrapping", which means being so mean as not to bother explaining to an idiot why they're an idiot in simple enough terms for the idiot to want to understand.