"Guys" is fine, except when it isn't. It's a pain point for some people, and it's reasonable to be sensitive to that.
> Yeah, and medieval oppression was actually real, unlike some other "oppression" I can think of.
That crosses the line into the ridiculous, and is precisely the kind of poison we should try to avoid. Oppression means longstanding cruel treatment or control. The author doesn't perceive longstanding class, gender and race based control and oppression over the last few generations in our society. That makes the author maybe not a great source to take advice from on the topic at hand.