He is shown to be a high-functioning alcoholic, but the movie glorifies his actions, rather than showing them in a completely negative light as it should be. Basis the movie, rage, entitled behaviour, and flouting social and moral conduct is considered to be the birthright of men - or at least this particular man.
The greater problem with the way the movie has been presented - especially the conventional happy ending - is that people fail to see the self-destruction that the protagonist experiences. They only view his 'passion' and 'heartbreak', not his misogyny, aggression, or general rudeness. Yes, creators have every right to present flawed characters - but not to put them on a pedestal.