Question: If you criticize Obama, you're a racist
I agree that the term "racist" needs to be defined more clearly to evaluate the argument. I see it being represented like this:
Person X is criticizing Obama.
Person X has <these traits>.
Racists have <these traits>.
Therefore, Person X is a racist.
Therefore, all people who criticize Obama are racist.
I see several times where a hasty generalization is used, mainly in making the leap "Person X is a racist, therefore all people who criticize Obama are racist."