Schneider was supposedly a major piece of the team's core, but with Luongo there, Schneider's presence on the team over the next 3-4 years wasn't that crucial.
If Benning did the Schneider deal, he would have been hammered here on these boards more so than Gillis was. There were strong rumors that Edmonton offered more (at the very least they offered the 7th overall pick, which would have GUARANTEED them Horvat or one of the guys drafted before him. At 9 there was no guarantee.
Regardless, I understand your point. I think what I disagree with is your perception that Gillis wanting to rebuild. It's kind of like having traded picks away and wanting to recoup some picks. At some point, you need to restock the cupboards. Keep in mind that they did trade away a 2nd that year for Derek Roy, a pick they could have used to select Yan-Pavel Laplante.