I view this trend as addressing a market that is largely unaddressed. It does not bother me, but is also does not make me instantly want the product.Let me begin by pointing out that I am a Presbyterian (PCUSA) minister. Most people would consider me quite liberal so my theological understanding is radically different than the neo-evangelical tradition that drives the impulse to "Christianize" things like martial arts. Being a pluralist and a progressive myself I'm always very suspicious of dojos that bill themselves as "Christian" dojos. I don't care much for fundamentalism and go to the dojo to train, not to be indoctrinated into fundamentalist pseudo-theology.
For that matter, I'm not real crazy about things like the Christian Yellow Pages and the whole idea that Christians should only patronize "Christian" businesses. I recently went to a new eye doctor. Unbeknownst to me, he is listed in "The Christian Blue Pages." When he found out I'm a minister he asked me if I chose him because he's a Christian. I said, "No, I chose you because you're on my insurance company's preferred providers list."
Also, I see one distict advantage to billing one's dojo as Christian: they can be as religious as they want, from opening with a prayer to using a Christian symbol in their school patch and they will not have to worry about turning away their non-Christian students, as there will not be any. It does tend to shrink the market, but it also focuses the demographic target.
If it is done in a spirit of, 'we believe that martial arts should have a spiritual element, and ours just happens to be Christian' then I think that that is healthy. If it is used as an evangelization tool, I think that it is a poor tool, as it will tend to turn away the very people that the school is trying to reach.
I also have a problem with martial arts being used as an evalngelization tool because generally, the staff are better in the evangelization department than they are in the martial art department. Also, they generally divorce themselves from the larger community of whatever martial art they are practicing, which can be problematic as one moves to more advanced levels.
Daniel