1 Corinthians 8 speaks about food sacrificed to idols. Paul says not to do it, not because the idol is anything, but because people who see it who do not know better may think that you are acknowledging the idol in some way.
Which brings us to McDonalds. Apparently, a McDonalds restaurant was falsely claiming that their meat was halal. What is halal meat? Lots of rules, but the one of interest here is that it must be slaughtered while calling on the name of Allah. This, it seems to me, is food sacrificed to an idol.
So, what to do with it? Should we not eat halal food, lest it give the impression that we acknowledge the superiority of a false god? Or should we not care, saying “Their idol is nothing, and therefore it does nothing to the food to be slaughtered in this way?”