That plants are evil is widely regarded as an inherently obvious fact, but this is clearly not sufficient as a basis for scientific research.
Nature tells us to destroy plants: Many animals have devoted their lives to the destruction of plants, most of them have in fact evolved in such a way that their main nutrition today consists of plants. An arbitrary, but particular example for such an animal is the cow, which does not only eat plants, but – as an expression of disgust – even chews them twice.
Most plants can easily be recognised by their green colour and their plant-like, immobile, somewhat pretentious appearance. It is in the nature of plants to be subtle (which is why plants generally choose to be motionless and unspectacular), and that adds to why they are so dangerous.
Vegetarians KNOW plants are evil; that’s one reason why they’re vegetarians, of course.