And this is why finding good maintainers for visible FOSS projects is hard.
You know what's unethical conduct? Misrepresenting someone's words in a way that make them look bad.
The maintainer did exactly what they usually do, I see absolutely nothing unexpected here, note that this was an unsolicited patch sent to a security mailing list. And this is typically how those are dealt with. To claim 'unethical conduct' is one small step removed from a formal complaint about the maintainer, and which is exactly the wrong message to send here. Witch hunts like this cause good people to leave FOSS projects. The maintainer could have given more credit but chose not to, that's the rules you play by when sending in unsolicited patches. If you must have credit then you should not contribute in this fashion.