I'm having a hard time here - do you really not see the connection between what I'm saying, what you're saying, and the use of a default masculine pronoun?
I see the connection, what I'm suggesting is that you knew what they meant when they said guy, meaning you did not need to suggest that they thought women didn't exist on the internet, nor did you need to suggest that they were assuming everybody on the internet is a man.
I don't think we're operating under the same impression of bad faith. You seem to be using it to mean "an argument or line of reasoning I don't find compelling", where I am using it to mean "bringing up a line of argument or discussion for some reason other than participating".
So to circle back around on this, some people feel like using male as the default gender is rude and exclusionary. Try assuming people are women, just as an experiment, and see what sort of push back you get. This isn't in any way a bad faith argument.