The hadiths may be talking about a Muhammad but not the Muhammad of the Quran. The Muhammad of the Quran was a preacher and a warner and a mercy for mankind and not some warlord and executioner. Killing prisoners is one of the ugliest thing a person can do and this is what the Taliban and Al Qaeda does and now we know why.
This is what the Muhamamd of the Quran did to prisoners*:*
6..8 And they feed, for the love of Allah, the indigent, the orphan, and the captive,-
At length, when ye have thoroughly subdued them,** bind a bond firmly (on them): thereafter (is the time for) either generosity or ransom**: 47.4
8.67-70. It is not fitting for an apostle that he should have prisoners of war until he hath thoroughly subdued the land. Ye look for the temporal goods of this world; but Allah looketh to the Hereafter: And Allah is Exalted in might, Wise. Had it not been for a previous ordainment from Allah, a severe penalty would have reached you for the (ransom) that ye took. But (now) enjoy what ye took in war, lawful and good: but fear Allah. for Allah is Oft-forgiving, Most Merciful. O Messenger. say to those who are captives in your hands: "If Allah findeth any good in your hearts, He will give you something better than what has been taken from you, and He will forgive you: for Allah is Oft-forgiving, Most Merciful
16:82 But if they turn away from you, your only duty is a clear delivery of the Message.
6:107 Yet if God had so willed, they would not have ascribed Divinity to aught besides Him; hence, We have not made you their keeper, nor are you a guardian over them.
4:79-80 Say:'Whatever good betides you is from God and whatever evil betides you is from your own self and that We have sent you to mankind only as a messenger and all sufficing is God as witness. Whoso obeys the Messenger, he indeed obeys God. And for those who turn away, We have not sent you as a keeper."
17:53-54 And tell my servants that they should speak in a most kindly manner. Verily, Satan is always ready to stir up discord between men; for verily; Satan is mans foe .... Hence, We have not sent you with power to determine their Faith.
88:21 22; And so,exhort them your task is only to exhort; you cannot compel them to believe.
42:6 48 And whoso takes for patrons others besides God, over them does God keep a watch. Mark, you are not a keeper over them. But if they turn aside from you (do not get disheartened), for We have not sent you to be a keeper over them; your task is but to preach
Thats the Muhammad of the Quran!
there are numerous examples of Muhammad of Hadith forving former enemies as well , you will not mention them as it does not suit your agenda.
But sometimes it was neccesary to shed blood and thats exactly what the Prophet did .....