1. Re-build these buildings out of gravel.
2. Underneath both buildings, dig holes just as deep as the buildings are tall.
3. Use cobblestone as a foundation for the buildings to keep them from falling by themselves.
4. Proper placement of TNT blocks.
5. Proper running of redstone.
If you lost a family member in 9/11 and you were trolling on the minecraft forums one day, you see this and click on it thinking it is a tribute to the lives lost and see comments like "add a plane" and stuff I'd be surprised if you wern't offended.
And you have it backwards, offending one person, not 7 billion (even though there isn't 7 billion people alive today) is enough for this topic.