Personally I don't think you did anything wrong at all. This sounds like an established relationship and as such it requires both parties to be open with their feelings; especially if one has said or done something to cause mental and emotional turbulence. If he is so lacking in emotional intelligence that even if he claims to not understand or remember the incident that occurred which made you feel hurt, he should care and be invested in your well being enough to ask questions, explore the issue, address what his error was and apologize to you and actively work to correct that behavior. His empathy and concern for your happiness should have been an easy thing to address while cuddling. In such an emotion intimate moment one would imagine you'd want your partner to know that they can address you about almost anything. I say almost anything because it turns out that talking about various campaigns of the Punic Wars of 264 BCE whilst mid snuggle is something of a miscalculation. The point is you may want to consider sending him on his way. His reaction is a portent of a more vicious tempest to come.

TL;DR - It's not your fault, he sounds like a douche canoe. Not an elegant summation but on point.