I would say "Yes, I don't like football." To be more precise, maybe say "That's correct, I don't like football." I know it sounds a little confusing so here is an example: Person A asks person B "Do you like football?" And person B responds "No, I really don't like it." Person A then asks "Really? You don't like it." And person b states "Yes, (or that's correct). I don't like it.

The correct answer is "no". :) It's the same as if you were asked if you liked football. Here's how it works! ^^ In both cases (if you don't like football), then your reply in a sentence is, "I don't like football." By saying "yes, I don't like football", you are actually contradicting yourself: you've given a positive, then a negative statement on the exact same topic. Only a positive-positive or negative-negative reply makes sense. In a simpler way, focus on the subject: liking football. In both cases, again your answer is "no". The thing to remember is that a question asked in a negative form is not asking for information, but confirmation. If you're really stuck, just forget "yes/no" and reply with a full statement.

A slang like "yep" would also work quite well, like "Yep I don't" people say the same thing twice when they are surprised, it's almost like they are asking for you to repeat yourself again, even though just "yep" is a proper response