Alright, I've had enough of this. There is zero evidence that plants feel pain. They do not have the requisite nervous system for such sensations. They lack a brain and other sense organs. I'm not a botanist, and it is evident that some plants are able to respond to the environment, but I am unaware of any mechanism any of them possess that would indicate sensory experience of any kind. Now, animals such as my dog very obviously feel pleasure, pain, etc... ; this applies to cows, chickens, pigs, etc...as well.
Unless there is some paranormal method whereby plants are able to have sensation(though, I don't know what good sensory experience would be to a carrot or a rutabaga), I can find no evidence for it. It is obvious to me that animals do feel things. Thus we should try to reduce that suffering since we can.
As for other animals not being sensitive to the pain of their quarry... That lack of awareness is their excuse. We don't have that excuse. Thus it's no good arguing it's the 'way of nature' to cause other animals pain, at least not with me.