I think the boyfriend's anger is justified. Considering that Eric and Ashley were long time friends, I bet the boyfriend was always suspecting something but Ashley would always deny it. Then low and behold, they are found making out in public. The fact that the boyfriend probably suspected it all along, but still loved the woman enough to propose, and then it ends up he's right, I would be reallllly fuckin pissed too. More so because he suspected it and she probably denied it and he had no choice but to believe her without proof. Maybe he did a dickhead thing, but I dont think he was a dickhead by nature.