The sad thing is that you don't even realize what you did wrong. It's not so much what you said as it is what you did and how you said it. Instead of blurting out, "You didn't even enchant your gear," and then quitting the group before he could so much as respond, you could have mustered up a little
tact. Better options:
- You're missing a couple of enchantments. Need advice on which ones to apply?
- There are some cheap <pick a color> gems for sale on the AH right now. Want to socket them? Even non-optimal gems are better than none.
- I assume you're in the process of adding item enhancements to your gear right now.
Then after making it known that you're aware of his deficiencies without putting him on the defensive you stick around and wait for him to respond. If there's no response you can step it up with something like, "I'm sorry, but I have a bad feeling about running with a group whose leader can't be bothered to apply minimal effort to enhance their gear. The cost of my repair bill will end up exceeding the cost of your missing enhancements." That way the response will be more on the order of, "Understood. GLHF," and less on the order of, "Go f--- yourself."
In fact, I always carry cheap gems around for such occasions. People are much more receptive to advice after they've been given a 10-gold-piece gem that fits a missing socket.