Grammatical (or grammar) pedantry syndrome is an illness or a form of obsessive-compulsive disorder where someone has a compulsive desire to correct any grammatical errors one has made and is obsessed with taking this peculiar, constant, and vexatious (from the target's perspective) action.
"Me and mark ate cookies!"
"You mean, 'Mark and I ate cookies!'"
"Stop it!"
"Sorry, I have Grammatical Pedantry Syndrome."
"If your statement was never supposed to be read as anything more than a synonym for 'Russia is not good and not our friend' then sorry for being comparably pedantic, I guess.
A state of mind which is about caring a lot about formalities, often more than necessary. One may be called pedantic when he/she points out corrections in unimportant details.
Okay okay, so there were five people there instead of four, no need to be pedantic. Now anyway...