The thing is, the Jolly Roger is his home. Ariel was asking way too much from him. How many of us would be ready to give up our home to help a complete stranger find her lover?
Killian Jones isn’t Prince Charming and he’s never claimed to be, so I’m not surprised he didn’t take her up on her plea. Though, I do think him killing Blackbeard was a rash decision made because Blackbeard was taunting him, and to also prove to himself that he was indeed the same person and that he hadn’t changed.
The fact that he was so racked with guilt 9 months later shows that he was only lying to himself and that Emma has truly changed him for the better.
It just bothered me when Ariel called him selfish when she was literally asking him to give up his ship for her so she could find Eric."
User Caitlin, in response to this question posted by The Examiner 3x17 recap - “Do you think Hook was acting in the name of love when he betrayed Ariel? Or was it just a matter of machismo?”
It defends Killian’s choice without taking away the unhonorable aspect of his act.