Basically, instead of seeing piracy as ‘freedom to attack whoever I want and take their stuff’, Luffy sees it in broader terms, as ‘freedom to ignore whatever boundaries or laws might hinder my ability to do what I want’, and he does take full advantage of that. He’s just not all that interested in attacking people who haven’t done anything to deserve it.
I can give you, comics and manga comparisons not being fair . But that still doesn't explain why spiderman and batman actually content with their opposition But supes just doesn't as often.