When is a Litmus Test Not a Litmus Test?

When G. W. Bush says it isn't. Of course he may never have had chemistry in school or read the definition in a dictionary. A litmus test is a test that uses one criterion as a determiner of a particular quality.
A determiner that Bush has chosen for picking a judge is that the judge will not "legislate from the bench". Of course the definition of "legislate from the bench" depends in this case on opinion that is well skewed to the right. If that doesn't constitute a litmus test I don't know what would.
What is wrong with having a litmus test? Wouldn't that include eliminating prejudice, irrationality, bias?
There are many judges that are considered to be competent in legal matters but may be irrational in some particular area. A judge swears an oath to be impartial, unbiased, and unprejudiced. Being picked to be a judge because you are biased, prejudiced, and partisan is contrary to good legal ethics; particularly for a judge in the highest court of the land.
The people do have some say in the matter and they should be demanding that if justice is to be served that it be from a court that is fair, unprejudiced, and non-partisan as well as competent.