There is actually no legal basis for a man having to prove his identity or right of occupancy to police in the middle of the night. I would agree that it's not surprising that a man who responded belligerently to this request was arrested, but that doesn't make the cops right or him wrong.

You can ignore race a factor if you want to. Professor Gates apparently felt he couldn't. I'm inclined to agree with him... simple reality is that a white man coming home in the middle of the night and having trouble with the door would have been far less likely to prompt a call to the police in a neighborhood like that in the first place.