But it is possible that he ought to have been cited as well? It doesn't matter if he's a hypocrite. The justification ultimately has to be, "Our paper did not use your work in any substantial way therefore a citation is not needed."
I can see how citations can get very complex for the purposes of scientific credit, traditionally there's a self-policed aspect to it in every academic community; however, in this century as advanced research gets more complex and globalized, it might be time for a more rigorous and neutral process of doing so.
I can see how citations can get very complex for the purposes of scientific credit, traditionally there's a self-policed aspect to it in every academic community; however, in this century as advanced research gets more complex and globalized, it might be time for a more rigorous and neutral process of doing so.