Actually it goes much further than this.
Of course, you're right. Other nations and terrorists would attempt to use the same tactics in an attempt to embarrass or assassinate W and future presidents.
It could also be seen as having rattled W prior to negotiations, if he had showed any weakness.
(Sidebar: In the past, the Russians were particularly adept at bullying negotiating tactics. They still are, when it suits their purpose.)
There are many subtle facets to diplomacy, much like a game of chess. Hidden agendas, one up-man-ship, tactics, and strategy all play their part. It takes great skill and courage to successfully navigate those treacherous waters. W is doing a fine job.