I only really need two reasons to hate PETA: Hypocrisy, and the complete denial of reality.
The first is rather obvious, such as how they kill the vast majority of animals they "save", or how many of their top people stay alive thanks to medicines developed through animal testing or that contain animal products. That they then have the gall to say "I need my life to fight for the animals" is rather sickening, when you consider they want to stop research that could be used to save countless other lives full of potential. They also seem to totally miss the fact that animal research also leads to new tools to better care for animals.
Of course, they don't actually care about the latter part too much. They don't want animals to be treated better, they want "total animal liberation". As in, their ultimate goal is for humans to have no interactions at all with other animals.
This is where "complete denial of reality" comes into play. The simple truth is, just like all the others, human beings are animals, and are part of the same ecosystems as all those other animals. In many places, humans hunting animals for food is the only thing that keeps the animal populations low enough that they don't eat themselves into the entire species starving. Domesticated animals like dogs, cattle, chicken, and turkey cannot survive without the aid of humans--they're no longer fit for a life that doesn't include us (though to be fair, cats and pigs would get along just fine).
The PETA Wonderland involves countless of species of animals simply all dropping dead. Because whether they admit it or not, humans are a large part of the ecosystem, and our activities are important to the lives of other species. We rely on them. They rely on us. That's just how the planet works. And trying to deny it is fucking stupid.
