Is an answerer abusing the Guidelines if he answers a question by using my name and defaming me?

There is one answerer who continually gives my answers a TD and has now disputed every point I made in a recent answer. The answerer went so far as to say in his answer that Pennybarr (me) is consistently wrong and to ignore my answers. This is always in the Health Category, sub-category Optical. My answer may have been overly cautious, but is it was correct. I research almost every answer I give and was in a high level hands-on management position in a famous eye hospital for amost 20 years.