Hanzou
Grandmaster
He fell down because he had really bad footwork. We have seen competitors from various styles including Tai Chi who have better foot work than that. We have even seen untrained fighters with better footwork. This guy is just not a good representation of Tai Chi or Chinese martial arts in general. This fight wouldn't have gotten the publicity that it's getting had he not boasted and claimed himself as a "Tai Chi Master." It's no different than someone claiming to be a Master in BJJ and then show up and perform horribly against someone who trained themselves to fight.
When someone beats another who claims to be an expert or master, then it damages the perception of the defeated system. The problem with TMA is that many people try to make excuses for the practitioner instead of just coming out and saying the truth. The fighter had no fighting or sparring experience and because of that lost the fight in a disgraceful way after claiming to be a Master.
My question to you as a practivioner of CMA; Given the media attention this is getting, what do you think happens to TCMAs if this guy keeps beating self proclaimed masters of Kung Fu? Do you think this could have any lingering long term effects?