I guess it would be something on the lines of one who looks down at Islam or Christianity but would read books by muslims or christians. Such a person would take what they deem as good and weed out what they deem as the otherwise. I am pretty sure such a person wouldn't look at this kind of action as compromise one's beliefs.

In short it is using one's judgement. The same kind of judgement one would use when reading a book of any kind.

To group completly different religions like Judaism and Christianity with Islam is doing a great injustice. Espicially in such a discussion for Islam doesn't have a "God vs Devil" ideal in its teachings. Islam and other religions have very little in common, aside from the fact they are considered to be practiced by monotheists.

In Islam every muslim man and woman are commanded to seek knowledge even if its as "far as China" as Prophet Muhammed SAWS has said. So I imagine when it came down to learning a fighting system a muslim would learn that and leave the rest. And by the way there is nothing of learning about other belief systems... it is the PRACTICE of "questionable" beliefs that muslims don't partake.

Peace
H