There's no absolute answer to that question. You could start with, would a reasonable person agree that the names rejected were likely too pre-disposed to defend Trump instead of chasing the facts?
If Republicans put up individuals with a reputation for more principled, independent stances, then rejecting them points to bad faith by Democrats. If they put up individuals that seem staunch Trump allies through thick and thin, then that signals bad faith by Republicans.
For me, it wouldn't even take a mythical paragon of impartiality to be acceptable, just someone that hits the low bar of "isn't likely to defend Trump no matter what".