Haha, good point, I had not considered that.

Based on his later replies, he is a reader of books (wow) and is proud of his knowledge, so no doubt he felt insulted by the "fundamental" point.

To snap was the only way he could come up with to save the face in front of his friends (not sure it was a success...). Not sure how you could have phrased your point differently so that he could choose to agree with you without damaging his self-esteem. He probably wasn't worth the effort anyway. People who aren't ready to politely face a little bit of confrontation should refrain from talking politics, especially on social networks.

Cheers.