In my mind, when people say "lads","guys" or "mankind", I just think "people". Does anyone really think they're litterally talking about men only? I feel like this kind of comment is just used to dismiss people.
From what you’ve said - in your mind, addressing a group of people as “lads” makes no comment on their gender. Some people will definitely agree with that and not be bothered at all. But I don’t find it even slightly hard to imagine that if I were a woman in a group being addressed as “lads” that I might kinda bristle at at, as I know some people do.
It’s just weird to me that anybody’s first reaction to this sort of thing would be to double-down on “actually guys is gender-neutral” instead of just thinking “good point” and making a mental note for the future.
Almost certainly, these people hate working class language, but they can't say that out loud, so hide it behind false pretexts.
I’d be intrigued to know who ‘these people’ are, though, as I am apparently one of them.
Maybe it’s because I’m not a native speaker. In Germany we have a huge gap between daily/ business communication and the communication from authorities. The latter don’t write „Sehr geehrte Studenten“, but „Sehr geehrte Student:innen“, so I suspect something similar is happening here too.