Yep, and the appropriate response should be via the legal system, not inciting an internet witch hunt.
Further, if you actually read what the artist wrote, the wording is actually quite polite and gentle. It is not threatening and does not incite.
Being a copyright issue the author is well within her rights to send a DMCA takedown and initiate legal proceedings, which is all the "spark" that is necessary for a timely and appropriate response.