You haven't got a valid reason to dislike the film if..
..It's because you think Jake LaMotta is a dick..
Yeh He's dick who has everything...and we watch him self destruct infront of our very eyes..
I thought it was compelling anyway..Scorsese always keeps it real, and we all know we've acted similar to jake at one point in our lives, whether it's on smaller scale or not..We're all capable of being Jake..
Maybe it's not everyone's cup of tea but i love seeing these films were the protagonist goes from extreme to the other..
You can't help but feel sorry for him when he's in the jail cell bawling..man..