We can't stop all suffering, but that doesn't mean we shouldn't stop any. There is currently no reason to believe that plants experience pain, devoid as they are of central nervous systems, nerve endings, and brains. It is theorized that the main reason animals have the ability to experience pain is as a form of self-protection. If you touch something that hurts and could possibly injure you, you will learn from the pain it produces to leave it alone in the future. Since plants cannot locomote and do not have the need to learn to avoid certain things, this sensation would be superfluous.
Plants are completely different physiologically from mammals.
Unlike animals' body parts, many perennial plants, fruits, and vegetables can be harvested over and over again without resulting in the death of the plant or tree. If one is concerned about the impact of vegetable agriculture on the environment, a vegetarian diet is still preferable to a meat-based one, since the vast majority of grains and legumes raised today are used as feed for cattle. It's fine for you to believe in animal rights, but you shouldn't tell other people what to do. Everybody is entitled to their own opinions, but freedom of thought does not always imply freedom of action. You are free to believe whatever you want as long as you don't hurt others.