There are many videos out there where you can clearly see (and hear) people in the foreground witnessing the second plane hitting. In fact, I've even linked a vid in the past that showed a compilation of many videos showing just that. It would be IMPOSSIBLE to cgi up all of those vids. Then again, I linked that vid before I put a moratorium in place on enabling mental patients.
This is absolutely the dumbest theory in a long string of really dumb theories you truthers throw out.