Which green creature can profitably block that doesn't die to bolt, costs less than four mana and isn't named Kitchen Finks? By the time the green deck has four mana, Goblin Guide will have already done its job. People assume green trumps red because its creatures are bigger. With red decks, creatures are only part of the puzzle. When they reach single digits, burn can and will finish opponents off. Cards like Brimstone Volley deal a quarter of life, so it doesn't even require that much.
Are we playing the same cube? White has Thalia, Mother of Runes, Oblivion Ring, Eight-and-a-Half-Tails, Hallowed Spiritkeeper, Unexpectedly Absent, Tangle Wire.