OAKLAND — A You Tube video showing a fight between two AC Transit bus riders has ignited a flurry of online debates about violence, race and the safety of public transit. The video, which shows an older white man exchanging blows with a younger black man, is attracting hundreds of thousands of hits. The fight took place Tuesday afternoon on a bus in downtown Oakland, near the corner of Harrison and Webster streets. We will update this story when further details are available.