Your lack of certainty should be a weight to the importance of making a public declaration of the incorrectness (that your perceive). As should the significance of the perceived errors, of course.

Pedants are often perceived as nuisances. They tend to have exaggerated certainty. This contributes to a pedant over-estimating the importance of a correction which can lead one to publicly declare such despite it's insignificance to the actual content of the discussion. See also: nitpicking.

Asking "Shouldn't it be 'whomever'?" in the Chatterbox seems a more appropriate approach for this particular distraction. Though, it appears that fewer would have been amused by you in that case.