I'm not disagreeing with you... Quite the opposite. I think the impact is fairly minimal in relation to everything else.
Brian wrote this today: http://mgoblog.com/content/open-letter-larry-dude-scheduling-michigan-basketball
He uses Minnesota as an example of good scheduling and I'd be outraged if Michigan played Minnesota's schedule. U-M aggressively plays conference tourneys, neutral site games, home and homes, etc. Those are all things that we want them to do. They are also things that many programs don't do (when was the last time OSU played a non-conference tourney? how many games did Minnesota play at home last year?)
Minnesota's schedule last year was a joke and they got lucky because 3 teams that were > 200 the year before made big jumps.
Look at Michigan's schedule this year... Maui over Thanksgiving, @ UNC the next week, Big Ten games Dec 2nd weekend, UCLA at home the next weekend, a trip to Texas mid-week. When Michigan is filling in the gaps it is clear that Beilein is more worried about timing, logistics and money and isn't worried as much about 'gaming the RPI' because if you win your big non-conference games and your Big Ten games the rest should take care of itself.
From my perspective, I don't think there's a season where Michigan has missed the tournament, been dramatically under-seeded or anything like that because of its NC-RPI.