A point well made, Rathpig, and one that strikes at the heart of Islâm. It DOES prohibit change. Change takes place all the time, but it specifically forbids this, with (undoubtedly apocryphal) ahadîth of Muhammad damning to hell those who introduce innovations into religion. Bizarre, considering the collation of ‘revelation’ verses into a written Qur’ân represents innovation itself!
Islâm, through the actions of Muhammad (remember, the ultimate example to follow), fully supports slavery. Now, in the west I never encountered it but that comes down to secular western laws forbidding slavery. Consequently people in this country grew up with an anti–slavery mindset. As for the founder of this religion, though, ‘authentic’ ahadîth attest to Muhammad owning slaves (
here, for example, in the middle of the 4th paragraph), having his slaves flogged (
here, though the punishment doesn’t quite take place in this example), and giving slaves away to friends and family (
such as here).
If he actively did this then, as you so correctly point out, Islâm endorses this despicable practice and muslims should abandon it immediately. BUT… if you discard one aspect of the religion then why keep any other? And can it really stem from god if you can ignore the bad bits and keep whatever good you find in it? And if you explain it away by tying it to the context of the time (everyone had slaves then, everyone took child brides, etc), then you can hardly call it a universal religion for all times, can you!