I have no problems with your principles (no forwards, esp. rookies on the PP) being more important than results on the ice this season. You never know, they might come in handy as the season progresses.
A solid argument can be made that sending him down is the right thing (I haven't liked other areas of his play this season). I also trust Gainey and Carbonneau's professionalim and judgement (they have alot more information to base their decision on).
I'm sure that they seriously pondered his performance on our lagging PP in coming to the decision (Carbo has mentionned earlier this season to the media that Sergei's PP performance was the reason he wasn't being scratched).
This team needs a shake up. The trade for Schneider, Kovalev sent home and Kostitsyn sent to the minors. Both players in this case were not giving a full effort. True that others aren't having a good season either, but few would clear waivers so it was the right decision to send young Kostitsyn to Hamilton. Again, IF (and that's a big if) Perron is right about his allegations on Kostitsyn, Price and Higgins, the message is loud and clear to everyone that it's time to turn that season around and although some have paid, others will take notes I'm sure.