It's one thing to bunt for a base hit, it's another thing to do a sacrifice bunt, which that clearly was. At the time it was 3-2. The goal was to get the runner to scoring position so a single from Overbay or Lee would tie the game. Then you worry about the winning run. Apparently they didn't want Clark to try to steal second, so they were willing to give up an out to get that runner to scoring position. The problem occured when Spivey botched it. That got Clark out, but they still needed to get the runner to scoring position. So Spivey then had to attone for his mistake by stealing the bag. All in all, this seemed to kill all momentum, but I would assume that's the logic behind it.