What a strange word to use in that context, why would he need to be forgiven by you? How has he wronged you? Seems at worst, an honest mistake in a complicated topic.
You're not using "at worst" correctly. What you describe is an "at best". Worse would be that CGP Grey deliberately picked a misleading title in order to optimize views, algorithm, etc.
This is, I think, the case. But I don't begrudge them too much, YouTube is cutthroat.
Maybe GP is a non-native English speaker? This construct would be pretty common way for a native French speaker to say they are angry at something. Not sure if it's common in English as well.
Yep, it may be more common in some English-speaking cultures, but in the midwest of the US it's extremely common to say stuff like, "I'll never forgive him for <thing>" and it's not meant to be taken literally. A more literal translation would be, "I'm very disappointed in this person's decision to <thing>."
