Correct. One team in the NBA wins the championship. You think the Cs organization should settle for "pretty good"? Think that's how they won 17 championships?
They certainly didn't do it by pulling off crazy trades that make the team worse.
Yes -- it would be rather difficult to win championships by making your team worse.
Historically, the Celtics have made plenty of aggressive trades that have contributed to them winning championships. If you think this trade makes the Celtics worse, so be it. But the Cs weren't able to win last year, and the team has not improved this offseason while a number of other teams have. So I've no problem with the idea being thrown out there, particularly when it involves one of the best players in the NBA.
The reality is of course that the Cs won't trade Garnett or Paul Pierce -- at least not yet. Hard to imagine Ray being traded either. Clearly Wyc's objective is to continue to take the odds that this team can find a way to get over the top despite their narrowing window of age.