gluglug

elda, I see your points. The situations weren't exactly the same as you pointed out and Dean behaved worse than Luke did.

However, Luke and Dean were both rebounding from their then unrequited love for the Gilmore Girls by marrying the wrong girl.
I still think on an unconscious level, Luke identifies with Dean's mistake and it makes him uncomfortable.

I'm thinking of last season's drunkDean "Why didn't she love me?" confession and then the scene where Luke and Dean are in the arcade when Dean is talking about his marriage and pretending to be happy.
Luke knew where Dean was coming from, even though nothing was said.

Last season there was a lot of Luke/Dean parallel and it would be good character growth for Luke to admit that he understands where Dean was coming from instead of acting like he's beyond reproach. As much as I love Luke, he does tend to act like that.

I'm not defending Dean, either. The guy is obviously screwed up and treated Lindsay horribly by cheating on her. And keep in mind that Luke didn't cheat physically but he couldn't commit to Nicole b/c his heart was with Lorelai.