If you would just read the verse in context, and quit accusing or arguing with people when you don't need to, just because they are not Adventists, the text would sound much different:
So Luke 9:50 certainly is anything other than "black & white."
Another way we can see that your black & white rule doesnt apply is here:
It does not follow, that these different intentions of the preachers should hinder the spreading of the gospel, and therefore it should not abate either your confidence or mine in the cause of Christ, since, by the overruling providence of God, that is carried on, both by the one and the other; not only by those who in truth preach the word faithfully, Jer 23:28 Mat 22:16, from a principle of love, (as before), to the same good intent with myself; but also by those who, though they act (as in Phi 1:15) out of envy and ill will to me, for base ends under a fair show, 1Th 2:5, yet they occasionally and accidentally, not by any direct causality, do promote the interest of Christ.
Sounds to me like maybe Jesus and the gospel have other colors besides "black & white" in the mix.