I don't think it's a double standard. Most people would not be unhappy that he was punished to the full extent of the law (although generally I dislike "example

I don't think it's a double standard. Most people would not be unhappy that he was punished to the full extent of the law (although generally I dislike "example" cases that are treated more harshly) if all of those involved were pursued, including those at more senior levels in the bank who were aware of and sanctioned the actions. You would not, by contrast, see prosecutors stop pursuing the top level drug dealers just because they got somebody to make an example of publicly.