Re: Sex with slaves
^ Well it makes sense when we are in a practical situation (that is when we are there at the moment and at the heart of the problem). Many things in Islam makes sense only when you look at the bigger picture. Slavery has been dominant since earlier times. The time of Moses (A.S) or earlier ... I think these laws are the same if not a bit altered to the one in the bible (Old Testament) given to Moses (A.S.).
On the brighter side the system of slavery was slowly abolished by the Muslims ... I think it was Caliph Umar (R.A.A) who had majorly removed the slavery system.
Things may not convince you at the moment, but i urge you to research on it further and look on it as practically and historically. Inshallah Allah Taala will guide us.