I totally agree with you. 中正紀念堂 is a historical site and should not be tempered with. It losts its historical value somewhat already when the 牌匾 is changed.
The sadder thing is that when Ma is elected as precident (if he is), he will change the 牌匾 back to original wording; thus whenever there is a change of party in power, the 牌匾 will change back and forth...