Remember, this is a person who:

is believed to be “part of” enemy forces within the meaning of the AUMF;
has been on notice for a lengthy period of time that he is regarded as such, is clearly aware of that, and has not only not denied it but actively taunted U.S. forces about their inability to get him;
has not made any attempt to surrender;
is believed to be playing an active, operational role in attacks against the United States; and
is camped out in a country that is unable to exercise civilian authority in the region in which he is located.

I don't think hand wringing is required here.