Debate is good!
I totally agree on the copyright thing – I only use my own photos now, or I pay others for copyright use. I once drew the racehorse Frankel as a bit of a trial in equine pencil, and then someone wanted to buy it, so I eventually uncovered that The Racing Post owned copyright!
They were kind enough to let me sell it without any cut for themselves, but only the original, no prints allowed.
Besides, if you work from other people’s photos, the creativity is theirs. This is one of the reasons I amalgamated the riders and the components…to get away from a simple photographic image.