I've just known and seen too many people who study "tai chi" or bagua who can compete in these type of contests. I think most of this debate about cma is a matter of ego. If it weren't so, people wouldn't need to prove that the art they practice was effective.
Windy asked how we knew which art the competitors were practicing. I.e., why do we say that it's a tcc or bagua guy against an mma or some other guy? It's true. Why is it necessary to label the guy's art? He gets into the ring and he's going to be doing what the other guy is doing. That's what happens. Though, it does not seem to be what people want to happen. Bagua practitioners want to see bagua; tcc people want to see tcc, etc. It doesn't make one bit of difference if, as someone pointed out, the competitor can't defend or attack with the practice they have learned.
People argue about empty force when, at a time when almost everyone over 10 has a video camera in his pocket, there are no examples of effective imas in competition with other martial arts that everyone can agree on. Most people want to see and talk about full contact, not empty contact. Many people who were interested specifically in that type of work have simply given up trying to talk about it.