Hell, I live in Indianapolis, just a short distance from the Speedway, and I was watching the race from home. It really wasn't all that shocking when only the Bridgestone cars started--rumor had been going around since before the race that the Michelin teams would boycott the race or not race once they were on the track.
It really isn't Michelin that is to blame. They simply advised the drivers that if they didn't fill their tires up to standard air pressure, then the tires would blow out in the more extreme turns. Of course, F1 pit crews tend to lower air pressure in the tires for better traction, but then this leads to blow-outs in the turns. The F1 teams that used Michelin tend to use this exploit to their advantage (the traction), and therefore boycotted the race once Michelin gave them a slap on the wrist for doing so.
But, yep, Tony George and all of those Europeans/Brazilians are going to be pissed now.