I see nothing in that article that shows the birther movement (again, no matter how stupid) was based on racial reasons, other than certain people's opinions that it did.
What else was it based on though? Honest question, to my knowledge there was never ever any similar issue raised for any president before and there seems to never have been any really good reason to doubt he was born here, no you, except that one. So I don't really think it's just opinion but the only logical conclusion to why this was started, no?