Wrong. They engaged in a logical fallacy, full stop. The correct response would have been for them to replace the boy with someone who wasn't so prone to lying (and for your clock example, replace or fix the clock). They must check every alarm raised from their designated "wolf watcher".
Interestingly, a good usage of an ad hominem would have been the argument for replacing the boy (e.g. "It's too inefficient to use him as the watcher because he's a liar").
While the article praises the iPhone interface and points out several of Android's user interface elements are very similar to solutions also adopted on the iPhone (to be fair, my 128K Palm Pilot arranged apps on a grid, a feature I am almost sure it copied from the Newton, just like about every PDA/smartphone), that's beyond the point. Windows Phone seems very non-iPhone-ish and there is a non trivial possibility Microsoft can actually bring out a decent mobile user experience after more than a decade of miserable failures.
I won't hold my breath, however. I too find it most incredible Microsoft finally hit something.
I keep in mind the fact that Barack Obama is an elected member of the Democratic party when he tells me to vote for a Senate candidate. It doesn't invalidate his opinion about that person, but it certain factors in.