I don't see what people's problems with this is. It says right in any warranty that any participation is a racing or timed event voids your warranty.
Seems to me that people are bitching because they're getting caught -- not because of the policy. The policy has always been there.
I do understand people's problems with Subaru doing the same thing; but that's only because Subaru also gives you a free membership and information on the SCCA, essentially telling you to do something that will void your warranty.