What should we think when an institution which champions modern architecture is about to destroy an example of it?

According to the April 12, 2013, issue of The Wall Street Journal (“MoMA Tear-Down”, by Jennifer Maloney) and other news sources, by the end of 2013 the Museum of Modern Art will demolish Tod Williams and Billie Tsien’s 2001 American Folk Art Museum building so that it can build an extension in that space. What should we think when an institution which champions modern architecture and its protection is about to destroy a unique example of it?