The name William has no commonly accepted or used meaning apart from as an identifier. I have no problem calling anyone by whatever identifier they choose, so long as they aren't asking me to apply an incorrect definition to that word.

The OED defines "guys" as a word used to refer to a group of people (male, female, or mixed). So if you ask me to not use a word because you refuse to accept its definition, that's very different to asking me to not use a word that is purely an identifier.