I thought Reza Aslan was pretty decent when I first came across him. But he said a number of things which were just ridiculous. I noticed him making things up, more than a couple of times, and I just can't take him seriously anymore.
Aslan sounds pretty reasonable at first, but then he says things (like his claims about Mohammed outlawing slavery) which make you realize he has no compunction about distorting or misrepresenting the facts, as long as it comports with his vision of 'the deeper truth.'
That's how religious texts (and hadith) are formed. Nobody has much compunction about lying and forging when it just restates and supports what the believer holds to be the Sacred Truth. Ironic that the Sacred Truth is thus built on lots of Sacred White Lies.
I guess the upside potential is that perhaps, as Aslan claims, a new Islamic Reformation is being conducted in precisely this way, with a bunch of lies and half truths contriving a new religion from the detritus of yesteryear. In this new religion, why shouldn't Mohammed ban slavery, and also declare the universal equality of women? Why not, if we're just making this stuff up? Let us emulate the glory days of the Abassid caliphate, 9th century, and just start formulating/reinterpreting new hadith to express these timeless historical truths.