Casual sexism finds it okay to address a group with females with, “Hey guys!” but finds it weird or degrading to address a group with men with, “Hey girls!”
“Casual sexism” uses the male generic just like pretty much every other European language.
Is that comment supposed to disprove the sexism in the OP? Because it doesn’t. Think about WHY most languages use the male generic. Because to be male is the default in a patriarchal society. Here is a good article explaining this.