Well, 'pedants' doesn't have to be a possessive here (it needn't be analogous to 'Speakers' Corner', although that is of course the most common pattern), but your assumption that he omitted the apostrophe where one pedant's possessive's apostrophe would have belonged, rather than where the correct apostrophe to denote several pedants should have been placed, is unsafe, anyway. :)
Well, 'pedants' doesn't have to be a possessive here (it needn't be analogous to 'Speakers' Corner', although that is of course the most common pattern), but your assumption that he omitted the apostrophe where one pedant's possessive's apostrophe would have belonged, rather than where the correct apostrophe to denote several pedants should have been placed, is unsafe, anyway. :)