It's his choice. If he felt so strongly about some internet argument that he had to delete his account instead of taking a break, then what can you do. This should be a place for everybody and we're not all going to post in the same way, express ourselves in the same way, or get along all the time. Sometimes that proves too much for some people.
I do hope he reconsiders though cuz it's like losing a friend in a way, but apparently he didn't feel the same.