I was very surprised to log on line last night and read that Phil had WD from the tournament after a poor round. I think its safe to assume that 99% of us on here would be taken to the woodshed by our boss/co-workers if we pulled this at work, "I was on vacation last week and I'm so mentally fatigued from it so I am going to tap out for the rest of this week, besides, the big presentation isn't due for a few weeks so its ok, etc".
IMHO - "unsportsmanlike" was a good choice of wording....Phil has long been lauded for being the consummate professional/fan friendly, etc etc, but this is going to go down as a teachable moment to your kids as what NOT to do. It is impossible to always have your A game , or to always have a great day, but showing up, working through it, showing some mental toughness is what sports is all about......because maybe that next day your swing clicks again.
But then again, you are playing golf - on a beautiful course, at Jack's tournament, nice weather, apparently the best milkshakes anywhere......I can't think of a better place to be able to deal with a little mental fatigue than that, suck it up Phil.