Facing Daleks who are constantly threatening to exterminate you is one thing, facing Daleks who want to correct your grammar is something else entirely. Something worse.
Could you imagine if your high school English teacher just hovered nearby, pointed her finger at you, and just repeated “CONJUGATE!” over and over again in a creepy voice? It would be akin to torture, and it’s exactly what a Grammar Dalek would do. Wear this shirt but don’t act like a Grammar Dalek or you’ll be associated with another word that starts with a “d” and ends with a “k.”