I agree that Kyubi is supposed to be the "baddest MOFO out there" (Bluedemon trademark ), and each time free Kyubi appears, due to his tremendous strength, I can understand he destroys everything. Look at Bee's comment this chapter with the eight tails. Here it's not an argument wether Kyubi is sinister or not, just that if he goes outside, I just assume he just destroys everything willingly or unwillingly.
Another thing, which part of Kyubi chakra is stuck in Naruto? Yin or Yang? I don't remember which one. Nevertheless, if the "bad" or "dark" one is in Naruto, that may explain why Kyubi said his chakra was sinister.
Despite all, I still think Kyubi is a wicked beast.
I'm waiting for Bee to pollute the water pool with liters of ink ^^