Like so many others on here, I've been rewatching, from episode 1 up to the last episode, getting ready for the final season. Beginning in Season 4, I started to realize that there's no actual evidence that Charles Widmore is really going to kill everyone on the island, or that he has evil intentions at all.
Everything we know about him "wiping everyone out" comes from either Ben, who lies about everything, or Keamy (end of Season 4 when he opens up the safe and reveals the "secondary protocol"), but Keamy has gone crazy at that point, either from the island's effects, PTSD or just revenge. We have no evidence that we've seen that Charles Widmore has bad intentions.
In fact, it appears that Ben has been a false leader all this time (according to Richard, the leaders are chosen very specially, but Ben appears to have politcally maneuvered Charles into getting somehow exiled) and that Charles is a rightful leader according to whatever mystical things are going on on the island. Good indicators of this: the baby/mother thing didn't start until Ben took over, Jacob gives Ben the cold "What about you?" in the final episode, and Ben never appears to have actually spoken to Jacob and didn't even know where to find him.
As for the cryptic "rules" and why Ben and Widmore say they can't kill each other, I suspect that's just the "Others aren't allowed to kill Others" thing -- remember, they were going to put Juliet to death when she killed Whatshisname in Season 3.
So, in sum, I think Widmore is the rightful leader of the Others, tapped into Jacob's will, the island's magic, etc. and that Ben, this whole time, has actually been the bad guy.
Everything we know about him "wiping everyone out" comes from either Ben, who lies about everything, or Keamy (end of Season 4 when he opens up the safe and reveals the "secondary protocol"), but Keamy has gone crazy at that point, either from the island's effects, PTSD or just revenge. We have no evidence that we've seen that Charles Widmore has bad intentions.
In fact, it appears that Ben has been a false leader all this time (according to Richard, the leaders are chosen very specially, but Ben appears to have politcally maneuvered Charles into getting somehow exiled) and that Charles is a rightful leader according to whatever mystical things are going on on the island. Good indicators of this: the baby/mother thing didn't start until Ben took over, Jacob gives Ben the cold "What about you?" in the final episode, and Ben never appears to have actually spoken to Jacob and didn't even know where to find him.
As for the cryptic "rules" and why Ben and Widmore say they can't kill each other, I suspect that's just the "Others aren't allowed to kill Others" thing -- remember, they were going to put Juliet to death when she killed Whatshisname in Season 3.
So, in sum, I think Widmore is the rightful leader of the Others, tapped into Jacob's will, the island's magic, etc. and that Ben, this whole time, has actually been the bad guy.