Who is clean and who is unclean?

Lev 13:13-14 read:

Then the priest shall consider: and, behold, [if] the leprosy have covered all his flesh, he shall pronounce [him] clean [that hath] the plague: it is all turned white: he [is] clean. But when raw flesh appeareth in him, he shall be unclean.

I have been wondering about these verses for few days. Why would God consider a man covered with the leprosy all over his flesh clean? On the other hand why would God consider a man with some raw flesh unclean? I would think that the former is more unclean than the latter. However God says the former with leprosy all over his body is clean and the latter is unclean.

Matthew Henry said:

If the eruption, whatever it was, covered all the skin from head to foot, it was no leprosy (v. 12, 13); for it was an evidence that the vitals were sound and strong, and nature hereby helped itself, throwing out what was burdensome and pernicious. There is hope in the small-pox when they come out well: so if men freely confess their sins, and hide them not, there is no danger comparable to theirs that cover their sins. Some gather this from it, that there is more hope of the profane than of hypocrites. The publicans and harlots went into the kingdom of heaven before scribes and Pharisees. In one respect, the sudden breakings-out of passion, though bad enough, are not so dangerous as malice concealed. Others gather this, that, if we judge ourselves, we shall not be judged; if we see and own that there is no health in us, nosoundness in our flesh, by reason of sin, we shall find grace in the eyes of the Lord. 

2Cr 12:10 reads:

Therefore I take pleasure in infirmities, in reproaches, in necessities, in persecutions, in distresses for Christ's sake: for when I am weak, then am I strong.

May I find grace in the eyes of my LORD!