'hält dagegen' = counter argument.

Gegen was? Usually it means, that you bet against the opinion of somebody else. For example, your friend says: "I bet 5 dollars, that I can eat 10 bananas in two minutes", you could say: "Ich halte dagegen", meaning, that you don't think, that he can do it and you are willing to take part in the bet. Your quote is a bit out of context, but maybe that's what it is about?