But not accurate? I doubt it. If the movie was accurate, not at all accurate. How about Al Capone or Bugsy Siegel? They were certainly equal opportunity thugs. And on, and on.
Capone, Segal, et al were openly ethnic. They didn't claim that their gods allowed them to kill "others".
There were wars between Italian, Jewish, Irish, and other gangs
(Jewish here meaning a group set apart by their relegion, not acting in accordance with that relegion - a perceived 'nation').
There were periods of cooperation among all these as well as black, largely protestant, gangs.
None of these groups was following a relegion when they acted as criminals, and few if any claimed otherwise.
I expect that many did use their relegion as a means to hide, to conceal, or to rationalize when necessary,
that's use of an available tool just like the Tax Codes were an available tool to bring them down.
In the end, they were just crooks who eventually got their due rewards and passed into history.
We still have crooks, very few of which would cite scripture as their defense.
Only Islam seems able to merge evil acts into relegion while transcending ethnicity (at least on the surface).