You said that "Just saying that blaming all whites is as bigotted as blaming all blacks for crime or all arabs for terrorism." I will agree with you but you need to disagee with the author's logic which is terribly bad. He says the exact opposite of what you said.
You seem to be reading that statement differently that I did. I read it to mean that if you discriminate against one person of a particular race, it is as if you have discriminated against all of that race.
In order for it to be exactly the opposite of what I said, it would have to mean if one person discriminates, it is as if all people of the same race discriminate. That seems to be the assumption of many, but it is not what the statement says.