Performance art is not what taekwondo is for and is bad for taekwondo. Aikido is a spiritual pursuit and people who leave the spiritual element out of aikido are missing the point. People who aren't really learning to fight are wasting their training and are diluting the martial arts.
These claims are all rooted in the same basic belief: that a martial art is for something, that it has an objective raison d'etre which is independent of the needs and goals of the individual martial artist. If your practice of the art does not serve this particular purpose, then it is wrong, and, even worse, it harms the art as a whole.
My favorite martial arts blogger, Rob Redmond of 24 Fighting Chickens, addresses this belief in discussing one of his blog entries:
Karate is not _for_ anything. Karate doesn't have emotions. It isn't a person. Karate is a concept, an instruction set, a gathering of principles.
The people who do the Karate determine what they do it for. That is where the purpose comes from -- from the people who do it. Each of them does it for a different reason.
Just because I do not do Karate for a particular reason does not mean the reason is invalid for you. It simply means that we are habituated to thinking about Karate incorrectly and speaking of it as if it had willpower and personality -- as if my doing it one way would affect the other way of doing it someone else practices.
That has come to us, I believe, from the group-think of organized sports, organized religion, and the Japanese culture.
"Gambling isn't good for baseball." What the heck does that mean? It means that the person saying it doesn't like what happens when people gamble. Baseball isn't damaged by gambling. Baseball happens all over the country whether anyone gambles or not. But his experience is lessened, he feels, if the players gamble.
"What is Karate for?" is the same sort of group-think question. Karate isn't for anything. Nothing is good or bad for "Karate." Karate isn't a person.
I'm with Rob. I think a martial art, like all forms of art, exists for its own sake (ars gratia artis). It doesn't need to have a point. It doesn't have to justify or validate its existence by serving a particular purpose. It is up to me to determine what purpose my aikido serves in my own life, and it is up to every other martial artist in the world to make that determination for himself. Their reasons do not invalidate mine, and vice versa.
This strips me of the authority to say that something is "bad for aikido". I can only speak for myself and my own needs; all I really mean if I say that something is "bad for aikido" is that it is bad for me.
This doesn't mean I don't have complaints about the way some people practice the martial arts; I do. Some people (like the belt-chasers I described in "Karateville") practice martial arts in a way that negatively affects my own personal experience of my art when I train with them. But I cannot be so arrogant as to presume my complaints are -- or should be -- everyone's. I don't have that authority. No one does.