There is no "correct" pronunciation. There are different books in different countries (with different levels of authority) documenting different pronunciations, but that's about it. The fact that it bothers you is odd. Pronouncing it as "daymon" is a way of signaling that you're talking about something very computer-related and therefore adds clarity to the language. And on the flip-side if you consider daemon and demon the same word (as it has historically been; see: https://news.ycombinator.com/item?id=16304452 ), then why is it that the spelling "daemon" (and not "demon") is used so consistently in computing? It's quite clear that within computing, the words demon and daemon are _different_ and the fact that they are often pronounced differently reflects that.

Language evolves. Get over it.