PETA doesn't want you cat or dog, they then will have to kill them, as shown above. They don't want you fish either, because they then have to flush them. What peta does is hilighting the terrible conditions under which fish are bred, kept and shipped to end users, killing 90% of all fish in the process. The want to stigmatise fishkeeping to the point where the average person becomes outraged with people keeping fish and ban it, just like smoking in public places.
PETA knows they can turn people's opinions, even if they need to launch campaigns that may take years to have an effect, these are skirmishes in a drawn out war that they know they will win with a high probability of success. That's why get the committed volunteers, and attract significant and sustainable funding for their cause.
We as an industry give them all the fodder they need, industry kills 90% of the fish it produces by merely moving it through the marketing channel. Monster fish end up in 4' tanks only to be released into rivers where they become an environmental calamity. Betta's are kept in jam jars. Fish in LFS are often kept in cramped dirty conditions, malnourished where they canabilize and scavenge on each other in order to survive, this is the issue that needs to be addressed. Railing against them only encourages them. Notable improvements and outcomes in fishkeeping need to be tangible and noticeable. Stop selling RTC to keepers with 4' tanks and telling this is good for life, I could go on and on...