Essentially Susan is trying to argue that Bob's action and/or argument is racist and hence by definition bad.

Too many guards were facing the wrong direction until now.

The problem isn't so much that connotations may sneak in, it's that relevance may sneak out. That's why I said some things were confused and not even an argument: the key step was that a label applied and everything with that label was invalid, and that thinking something is an argument doesn't make it so be it sentences or even a string of arbitrary characters, and so on.

It's too difficult and too costly in terms of accusations made and inferences drained from language to zealously guard against bad connotations.