The way I'm reading this article and Rosenthal's tweets, it sounds like he wasn't initially sure which of the two pitchers the trade was centered around. I might have missed it, but nowhere did I see that the Sox pushed for Buchholz in that trade.
Maybe the Sox did offer either Buchholz or Miley, and the Mariners chose Miley for reasons that have nothing to do with a disinterest in Clay, but even with that, that's not the same as the Sox pushing Buchholz.
As far as making excuses for Clay, I don't think anyone is trying to make excuses for his performance so far this year. He has not been good, plain and simple. People are just defending the decision to pick up his option, which was the right decision, regardless of how terrible Clay pitches this year.