Massive infringement of copyright of photographers' work

I belong to a Copyright Infringement Group of photographers and painters on Facebook.  One of our members alerted us to a massive infringement of copyright of a "painter" on Fine Art America, RedBubble and Imagekind.  This person who calls himself a "painter" had lifted at least 275 photographs he found on Google, placed a couple of Photoshop filters on them and passed them off as his work as "oil on canvas" or "acrylic on canvas" but the "original" was not available for sale.  The original, of course, was not "available" because it only existed on his hard drive. His "bio" was a joy to read - all BS of course but he has been exhibited in museums in Oklahoma, etc and has sold his "work" worldwide.  His pieces were derivatives of photographers' images where he has not sought permission to use their work and none was aware that their images were being used for commercial gain.  So we started to track down the legitimate source of his "paintings".  This was made more difficult due to the fact that few, if any, of the images we found were watermarked in any way.  (Please photographers, WATERMARK your work!).  I tracked at least a dozen photographers (many were in Flickr) and advised them of this copyright infringement and passing off.  All were appalled that their work was being used as a derivative and they started to contact him directly and demand removal of their infringed work.  As many of the photographers were impossible to track to legitimate source, I tried another tack with FAA and RedBubble.  I advised them that this "painter" was contravening their terms of use in that they were not "paintings", not "oil of canvas" or "acrylic on canvas" but simply they were photographs he had found on Google and he had Photoshopped and was passing them off as "paintings".  I also stressed to both FAA and RedBubble that they were risking their safe harbour protection if they did not address this issue.   None of the photographers I contacted had embedded a watermark in their work.  This "painter" even took a couple of Getty photographers' work and I emailed my Getty contact (when I was a Getty contributor) and advised her of this infringement.  No response there which is hardly surprising!  Ten days went by and today, I went to the FAA site and did a search of "artists" and lo and behold, his account had been removed.  Unfortunately, his "work" is still appearing on RedBubble but as RB don't give a toss about copyright infringements, I don't expect too much response from them.  They kept advising me to contact all the photographers and suggest that they send DMCAs to RB.  This was impossible as most of the time, I could not find the legitimate source of the image (lack of watermarking yet again!) so I tried the same tack I did with FAA in that the "painter" had contravened RB terms and that they were risking their safe harbour protection.  I won't hold my breath waiting for RedBubble to actually do anything in relation to this.

Update: I also wrote to the Print on demand site,  Imagekind and they have also removed his galleries.  Still waiting for RedBubble to actually do something.

Update: RedBubble has also removed his "work".