Would you say the way I used the word ignorant of myself was a derogatory way, gand? Or the way I used it of polymaths?
In any case, I didn't. I used it straightforwardly as meaning not knowing something or some things. There is nothing to be ashamed of in not knowing something, including words like mendacity and audacity. Those are not everyday words in most people's lives. Of course plenty of people won't know them, or might have come across them but not fully understand their meaning, and so might use them wrongly.
If you've never come across a word, you are ignorant of it. If you've never come across a certain wild animal, you are ignorant about that. If you've never heard of a certain artist, you are ignorant about that artist. Ignorance is not always derogatory. Most of it is simply not knowing. We are all ignorant to some extent.
If someone uses ignorant as an insult, they are just being a git.