Hello; All of us are keeping fish outside of natural conditions, that to some degree or other could be said to be cruel. However, I do understand the OP to be considering "cruelty or abuse" within the parameters of what might be called "good fishkeeping practice". Having read threads on this and other fishkeeeping forums, I must conclude the range of these practices is extremely wide. Search thru threads on such things as water changes, UGF, stocking density, tank size for particular fish and such.
That, so far, some group is not empowered to dictate to me about how I must keep my fish is to my likeing. I have seen many of the things cited thus far. Over the decades several folks have seen my tanks and decided to start keeping fish. I use to encourage them. The large majority of their tanks ended badly for the fish. I no longer give folks any encouragement and in fact make the hobby sound more difficult than it is.
I do agree that many fishkeepers, fish shops, breeders and collectors have practices that are cruel or abusive whether intentional or not. Even so I still do not want a watchdog, no matter how well intentioned.