Based on a definition of PII that does not regard IP addresses as personal data.
A definition that, of course, does not make sense and is not true. You worked on an abuse desk and you traced IP addresses all the time so obvious you know better. Some people really live in some sort of fantasy land where common sense does not exist and even well-known facts are dismissed out-of-hand if it somehow affects your "religious beliefs." People are traced all the time by IP addresses. Whether a specifc IP address is PII depends upon the facts of the specific situation and you obviously don't have time to evaluate each specific situation if you are getting large number of abuse complaints. Under these circumstances you should probably treat all IP's as PII.