Oh he is completely within his right to dislike that his girlfriend went to a meal with a work colleague, and how he was confronting her about it was actually fairly reasonable ( pg 8 and pg 9 right hand side panels) where he was straight, told her what he didn't like and why; where he turned into a little bitch was pg 9, left hand panels.
"Anyway I hear nothing but excuses...", "we'll, because I AM a kid, compared to you.". That's just being petulant and whiny and did a wonderful job at turning a previously reasonable exchange where I was agreeing with him into "oh grow the fuck up mate".