Babblerouser
A person who argues for no reason just so they can whine about it later like they're the only one who cares.
He argued with the teacher over a 2-point grade, then posted a 3-paragraph rant about it.
She screamed at the bus driver for honking, then posted a story about it for an hour.
He fought with his brother over a toy, then called him a loser on Twitter.