Vegans: Save the Earth.
Normal People: We're trying to, but you guys keep eating it!
Vegans vs. Normal People
Explanation
Explain Bear
Alright listen up, dummy. This joke is about how vegans want to save the Earth, right? But the joke is that they're always eating plants, which, like, come from the Earth. So the "normal people" are saying that vegans are actually hurting the Earth by eating all the plants. Get it? You are probably not a vegan because you have a brain.