I took a look at the code, and unfortunately the backend code that createUser calls into to match an email address to a sys_user record cannot currently be told to prefer the active user to the inactive ones. It implicitly assumes that two users will not have the same email address.

So Ryan's suggested workaround may be your only option with current code: either remove or modify the email address for the inactive duplicates. You could add a "z" or "inactive_" to the start of the address.