How can you fight the errors of the Church when it does not err, by definition? It is never wrong; it is the sole arbiter of what is correct and what is Christian. Thus to argue against the Church would be to commit heresy.
That, in my opinion only refers to matters of faith and dogma. Obama doesn't fall into either category as far as I'm concerned.
ONLY within, as some one else has already posted, certain limited sphere. For example, She can speak reliably on what a just war is in principle. She cannot with as much reliability say whether this or that war is just. She can say reliably whether or not or in what respects one might say everyone is due some kind of medical care. She does not say that the only or even the best way to try to give everyone his due is through the actions of a central government. There is PLENTY of room for debate.
Thus to argue against the Church would be to commit heresy.
Wrong again. To argue against her might be a good thing to do. It might help clarify teaching. However once she has spoken definitively on a matter of faith or morals to persist advisedly in holding an opinion contrary to what she teaches might qualify as heresy.
To make false blanket assertions about her without taking reasonable care to see if they are accurate is not heresy. It's not heretical to be irresponsible, to despise the truth, or to be imprudent. Wrong, yes; heretical, no.