The final frame in this comic portrays strong anger at rejection
No, it doesn't. It shows mild anger at being insulted for no reason. Are you running on the assumption that he's asking her out in this scenario? The only rejection he got was unsolicited. Like if I walk up to the next woman in the street, ask if she's single and when she says "yes" I respond "nevermind, you're not good enough". Now she's upset and understandably so.
I'm in full agreement with your point, but this comic is not a representation of that in any way.