Why are all of Obama's oponents accused of racism whenever they legitimately criticize Obama?

First Hillary and now McCain... This guy is immune to any criticism! I didn't hear any childish accusations of racism whenever Kerry, Gore, Bush, ect. were criticized by their opponents because that's POLITICS. This is sickening that you can't even say anything about this man without being chastised as a bigot. Everyone is walking on egg shells this election. This new breed of liberal youngsters are bringing their childish antics into politics. If this is the type of drama Obama and his people create, imagine what an Obama presidency would be like.