it's a sports term

Mainly because most people make the act about Cas himself, or make it about his relationship with Dean, rather than how it speaks to Benny and HIS character.

We see all throughout the Purgatory flashbacks that Benny does not trust Cas one bit, and spends a lot of his time antagonizing and questioning him. He has his reservations, and from an outsiders POV, one not blinded by a personal and biased history, it seems as though Cas (an angel) had left Dean (a human) to fend for himself.

Then we get to the fight scene against the Leviathans, where Cas is about two seconds away from getting his head ripped off when suddenly, Benny swoops in and deals a killing blow before anything could happen.

Despite the fact Benny did not like nor trust Castiel, despite the fact he thought he’d draw too much attention, despite Benny’s own PERSONAL feelings towards the guy, he chose to save him anyway because he knew just how much Cas as a person meant to Dean. It was his loyalty, his selflessness, putting another person above his own feelings and safety despite the fact the guy he saved wasn’t his favorite, THATS why Dean resurrected Benny. He kept his promises, he stayed loyal, and he became a good ally, so therefore Dean thought he deserved a second chance.