One can be considered an asshole while not being an asshole by many people's standard though. Anyone could find an issue with your behavior. Ethics and morality are not so clear cut. Plus, if behavior is an issue, one needs to specify that behavior, labels (such as "asshole") are extremely inadequate.

This right here is the reason code of conduct exists: so that everyone agrees on what kind of behavior is out of line before starting to work on the project.

As long as the behavior is adequately specified or described just like one would do in terms of behavior modification, then yeah, that works!

There's also the blatant irony that calling someone an "asshole" would be against a sane interpretation of the CoC.

Yup!