i think that those points aren't very kind, but are in many ways not only correct but expressing rightful frustration at (mostly white) students' selective memory for historical events/general knowledge, contingent upon whether or not they believe said information applies to them. like, i'd wager the average high school aged kid in africa probably has more knowledge of the scramble for africa (though they may not know it in normative u.s. textbook terms) than many u.s. students, despite a nominally more "developed" educational system. why? bc when you're living in a multiply-colonized society facing the material impacts of said ongoing colonialism every day....this shit is not avoidable. you know it whether you want to or not. meanwhile, many of those living in the imperial core - at least for now - can literally and figuratively tune out the violent realities that they (we) are party to + beneficiaries of. in a choice between being razzed for not paying attention in school, and having my community razed, enslaved, and stripped of resources in order to satisfy colonial greed....well, i'm gonna taking the razzing any day, even if it seems mean.
i also think the age dynamics here are worth noting: people say this to each other from adult to adult, typically because the ignorant adult claims that the u.s. educational system alone is at fault for their lack of knowledge (always concentrated around issues of empire and white supremacy and, curiously, never about the fandom they happen to be obsessed with....). except...no. because they're adults with an internet connection - the accusation that they were "doodling in history class" is a gesture at a broader set of decisions to remain ignorant & incurious long after history class/high school has ended. maybe your school taught you about the scramble for africa (most likely it was at least mentioned) and maybe not. but in a conversation between adults on a global internet, with free resources only keystrokes away (and in many cases bundled and handed to us by public scholars) the choice to "keep doodling" is an active one and a political one, and the blame rests on the shoulders of the privileged who refuse to learn about empire's "Others".