It was wrong for them to do it, and it is wrong for our guy as well. However, a lot of those letters were somewhat anonymous or refrained from speaking directly about Bush. Some of them may not have even been military, and some may have been discharged. But just because they did it, doesnt me we should either. There is a reason for the policy (to not give aid and comfort to the enemy), and if you break it, you are doing just that.
Sam, you obviously served when men were valorous and the leaders noble. The enemy is now in the White House and time is very short.