This is another shameful example of the confusion Hadith introduce to Muslims.
Let's remember that there are thousands of Hadith, and even the so-called authentic Hadith authors, admit they've done their best to compile what they believe are authentic Hadith.

The fact is that even Bukhari admits, even his collection may not be perfect.
Further, the Hadith quotes the sister (link below) has found completely change the fundamentals taught in the Qur'an of marriage and decency.

http://sakiless.blogspot.com/2007/05/on-troubling-hadiths.html

Chapter 22: AL AZL (INCOMPLETE SEXUAL INTERCOURSE): COITUS INTERRUPTUS

Book 008, Number 3371:

“Abu Sirma said to Abu Sa’id al Khadri (Allah he pleased with him): 0 Abu Sa’id, did you hear Allah’s Messenger (may peace be upon him) mentioning al-’azl? He said: Yes, and added: We went out with Allah’s Messenger (may peace be upon him) on the expedition to the Bi’l-Mustaliq and took captive some excellent Arab women; and we desired them, for we were suffering from the absence of our wives, (but at the same time) we also desired ransom for them. So we decided to have sexual intercourse with them but by observing ‘azl (Withdrawing the male sexual organ before emission of semen to avoid-conception). But we said: We are doing an act whereas Allah’s Messenger is amongst us; why not ask him? So we asked Allah’s Mes- senger (may peace be upon him), and he said: It does not matter if you do not do it, for every soul that is to be born up to the Day of Resurrection will be born.

So that’s pretty much what rocked my boat: I don’t know what people manage to rationalize as adults but as a child that was pretty damn shocking to me, particularly given what I was told by my Mother about the ‘morals of sexuality in Islam’.

The next few narrations in Sahih Muslim which touch on this as well:

Book 008, Number 3372: A hadith like this has been narrated on the authority of Habban with the same chain of transmitters (but with this alteration) that he said:” Allah has ordained whom he has to create until the Day of judgment.” Book 008, Number 3373: Abu Sa’id al-Khudri (Allah be pleased with him) reported: We took women captives, and we wanted to do ‘azl with them. We then asked Allah’s Messen- ger (may peace be upon him) about it, and he said to us: Verily you do it, verily you do it, verily you do it, but the soul which has to be born until the Day of judgment must be born. Book 008, Number 3381: Abu Sa’id al-Khudri (Allah be pleased with him) reported that Allah’s Messenger (may peace be upon him) was asked about ‘azl, whereupon he said: The child does not come from all the liquid (semen) and when Allah intends to create anything nothing can prevent it (from coming into existence). Book 008, Number 3377: Abu Sa’id al-Khudri (Allah be pleased with him) reported that mention was made of ‘azl in the presence of Allah’s Apostle (may peace be upon him) whereupon he said: Why do you practise it? They said: There is a man whose wife has to suckle the child, and if that person has a sexual intercourse with her (she may conceive) which he does not like, and there is another person who has a slave-girl and he has a sexual intercourse with her, but he does not like her to have conception so that she may not become Umm Walad, whereupon he (the Holy Prophet) said: There is no harm if you do not do that, for that (the birth of the child) is something pre- ordained. Ibn ‘Aun said: I made a mention of this hadith to Hasan, and he said: By Allah, (it seems) as if there is upbraiding in it (for ‘azl).”