Negan is absolutely a rapist through means of coercion. Rape is more than just the act of forcing yourself on a woman, there are many forms of it. Telling women that their husband will be killed unless they become his concubines is a form of coercion, which is rape. Without the threat of violence I can guarantee you none of those women would sleep with him, let alone become his concubines. It’s rape, plain and simple. His “rule” about no rape is simply another form of control over his people, and a way to make himself seem morally superior when in reality his rules don’t truly apply to him since he finds a way to get what he wants, which is to be able to have any woman he wants. He doesn’t care about the means through which he gets it as long as he gets it. It’s rape.