People react to the photos and movies because they have a connection to them. PETA has some pretty horrifying movies about farm animal conditions, but in general there is not a lot of sustained, widespread action because of that.
All of the people I know that had contact with farm animals are the least moved by PETA-like farm cruelty videos. They often shrug and say, "in my farm it's not like that".
On the other hand all of them are against seeing dolphin or whale cruelty even if only a handful of them ever saw any of cetacean (me included).
I know that this is all anecdotal evidence but it the most that I can produce.
Like many extremist organizations, they are effectively preaching to the choir. For somebody sitting on the fence, their approach to getting them on their side is to walk up to the fence, and smash anybody sitting on it with a baseball bat. Really amazing they have as much success as they do.
That reminds me when PETA tried to have whaling removed from Assassins Creed: Black Flag because they felt it glorifies the harming and killing of animals.[0]
My reaction was just like "Yeah, because killing whales on a game makes me want to buy a ship and start whaling myself."
