step on a rake
to say or do something seemingly uncontroversial which evokes an unexpectedly vehement response - akin to the experience of stepping on a rake in the dark such that the shaft swings up and suddenly hits one in the face.
He probably thought it would be an innocent remark, little realising he would step on a rake in view of the violent respnse it was likely to draw.
stepped on the rake
To run into trouble that could've been easily avoided if you would've just paid attention.
Boy: "My mom searched my room and found my stash!"
Friend: "Why was she searching your room?"
Boy: "I forgot to clean it like she asked."
Friend: "Sounds like you really stepped on the rake this time."
Friend: "Why was she searching your room?"
Boy: "I forgot to clean it like she asked."
Friend: "Sounds like you really stepped on the rake this time."