The owner of the Backpage in Lowell is upset about complaints posted online by a musician who stopped playing because he felt mistreated. Backpage owner Bob Ramirez called Matt Stubbs a “knucklehead” and a “crybaby” who spent as much time offstage as on it while at the bar. “[Stubbs] has played here a few times before and I always had to chase him around the club telling him to play,” said Ramirez. “That gets aggravating.” Earlier this week, Stubbs griped on Facebook that Ramirez was rude and condescending and, as a result, he abruptly stopped his show last weekend. His Facebook post was widely circulated among local musicians. Ramirez says he merely asked Stubbs to honor his contract. He said the singer started late and took lengthy breaks. “I don’t like to have to baby-sit people,” said Ramirez.