a person who is questioning their gender identity is allowed to say that they’re not comfortable with their birth name or that they don’t like certain pronouns. a person who is questioning is allowed to try new names and pronouns and ways of presentation. just because they are questioning does not mean that it’s okay for you to treat them disrespectfully and call them things they’ve said they’re uncomfortable with.
“you don’t know what you are yet so why does it matter if i keep calling you by that name?” isn’t a good excuse.
“you don’t know if that’s how you’re going to dress from now on so i can say how much i hate it all i want” is a shit thing to do.
a person questioning their gender identity does not make them someone who it’s okay to be an ass to. respect people who are questioning their gender identity the same as you would anyone else.