Since you're not a paying Contributor Level member, you can't add to a user's feedback rating. You can, however, post about your experience on the Board Of Inquiry (BOI). Ideally, people should use the search function to find preexisting threads to add to. There are already several threads for Keith Begin.
CLICK ME, to see a few of his recent threads.
Before posting on the BOI, you should familiarize yourself with the rules for posting on that forum.
BOI RULES. Once you're done with that, here's a link to the actual
BOI.