They're right, most people don't care about copyright when they stick one of their photos on a messageboard. Dina even regards it as extra publicity (I'm not sure if the person that shot the photos would agree btw), however anyone can claim copyright over their own work, regardless whether you perceive it as free publicity, that is simply beside the point.
At the very least the act of removing the watermark is a breach of copyright. Re-publication and copying of copyrighted material is a field of law on its own.