I'm tired of this

[Anno_Domini]

To be fair, I think you're just saying this because you're pro-Castiel. I believe Dean would have helped. Listen, the difference between AHBL and this scenerio is that Sam gave Dean his blessing before Sam jumped into the pit; Dean isn't as saddened as he was then and would've helped Castiel.

And also as I've said, Castiel said no to the brothers, he didn't want the brothers to help because he was ashamed of his partnership with Crowley. Still, Castiel was in the wrong. It is Castiel's fault. He said no out of pride but yet he's working with a demon.

[Harms]

I don't really blame Sam or Dean for not wanting to hear Cas' explanation. Dean made it pretty clear that they won't work for/with demons or monsters last episode.. Cas was right there when Dean said it. They also had the unfortunate experience of working for Crowley earlier this season and I'm pretty sure that they think no explanation can be a good explanation. Then they found out that it wasn't just Crowley they had been working for, but Cas as well. I'm sure they felt more than betrayed.

Sure, they may seem like hypocrites as some have said, but Cas and they both know how working with demons has worked out for them over the years.