I dislike Pinterest intensely and try to avoid it whenever possible. However, they do have a takedown procedure here...

https://about.pinterest.com/en/copyright

Obviously, in Mouse's pic, it's not Pinterest to blame, but whoever uploaded the image. It's easy enough to report unauthorised images, and I would hope there's some sort of 'Three Strikes' rule in place, so vigilance might pay off and the uploader's account is closed. But who has the time to scour Pinterest (or Imgur, Instagram, FB, Photobucket etc etc etc) every day...