This proverb is stated in the context of God's wisdom about leaders and kings. Therefore most likely it refers to those leaders who have gained and maintained their power through the shedding of much human blood. The key to seeing this is the admonition that such a man is not to be "supported." The idea behind this admonition is that one would throw their support behind such a man as their leader, which in their day would mean the king.
Ahab was a man who had shed much human blood. His power was maintained through intimidation and violent suppression of anyone who opposed him. He even allowed his wife, Jezebel, to act on his behalf to kill a man simply because he wanted his vegetable garden. When this happened, God sent Elijah to him because God had had enough of Ahab's wickedness and bloodshed. The Lord had Elijah tell both Ahab and Jezebel that they were going to come to violent deaths themselves. This is why we do not want to support violent men. The frightening aspect of God's judgment upon this wicked couple is that not only did they die - but their entire group of advisors were killed as well.
Another king who shed much innocent human blood was king Manasseh. His 40 year reign was marked by more bloodshed than anyone before him. Toward the end of his reign God sent a conquering nation against him and had him watch as his army was destroyed and he was taken into captivity. It was in a dungeon that he realized that Jehovah was God. He turned to God in repentance and brokenness - and God in his marvelous mercy forgave and redeemed this wicked king. God's favor came to him as he was returned to Judah as king. It was after this time that he removed all the wicked false gods from the land and returned to seek The Lord with all his heart.
When I review this I wonder, how could God support Manasseh after all the blood he spilled? The answer to such a question is found hundreds of years later in what Jesus Christ did by going to the cross. The fact of the matter is that Manasseh did not get away with anything. His sins (and ours as well) fell upon Jesus at the cross. They were paid in full in His death and resurrection. The only reason God supported Manasseh after he repented was because the penalty for his sin fell on God's Son instead. Thus what we have in Manasseh is an example of God's mercy and grace in the extreme.
There was another man laden with innocent blood who stands as the New Testament extreme of God's grace in Jesus Christ. His name is Saul - who later was renamed Paul. The apostle whom God used to write the majority of the New Testament - was another who deserved no support because he was laden with the guilt of human blood. Yet God showed him mercy.
Why would God show such grace to two of the most notorious men in the Bible laden with human blood. Paul answers that question in 1 Timothy 1:16 when he said, "Yet for this reason I found mercy, so that in me as the foremost, Jesus Christ might demonstrate His perfect patience as an example for those who would believe in Him for eternal life." God gave grace to these two men - one in the Old Testament and another in the New - as an example of his pefect patience and His incredible mercy and grace. If God can show grace to these men - we should take great comfort knowing that He can save us too!
So what do we learn from today's proverb? We learn that a man laden with the blood of men should not be our leader. We should beware when a man wants to rise to power on the blood of others. But we should also remember two, laden with human blood, who teach us of the depths of God's mercy and grace. We should remember that such amazing love is available to all who respond to the gospel of God's grace in Jesus Christ in repentance and faith. There is hope for all - even those laden with the blood of the human race. Hallelujah!