Agreed. If you're the author and Alice and Bob are the imaginary characters in your example, then you get to decide their gender.

Same as an author who is writing a novel, is free to invent characters and assign gender, sexual orientation, and any other character traits they want.

It's your story, they are your characters. You decide if it's a he, she, xe, or whatever.

You certainly haven't been keeping up with Twitter culture if you think this.

twitter culture is outrage culture. its a bunch of maniacs yelling at each other and they should all be ignored

Should, but aren't. That's the problem.

its the same people that are on twitter and then go to work and school and bring this with them. they should be ignored in real life too but nobody wants to deal with the hysterical accusations from the far left

What is this "Twitter culture" you're talking about? Could you sum it up?

most people on twitter and a lot of the verified people basically police each other for how "woke" they can be with social justice

and if anyone steps out of line against the insane number of rules about who you might slightly offend then you get mobbed and "cancelled" by being called a racist/sexist/bigot/transphobe/nazi and whatever cool word is in use until you lose your job and lifestyle and are permanently branded a terrible person