I think it's important to look at this from their perspectives, they have been doing this for a very long time, it's also important to remember that the women promote it just as much (according to one study more) then men, why would they continue doing his practice, because they firmly believe that it is better, they have also justified it with cleanliness and medical reasons.
we need to take a step back and look at what we do, is male circumcision really that different? yes the type III female circumcision is quite brutal, but the type I can be as little as removal of the clitoral hood, which is the exact same part as the hood of the penis. they use invalid medical advice to justify female circumcision just like we use outdated disproven studies to continue male circumcisio
I know this is going to sound extreme but that's because it's easier to look in disgust at another cultures barbaric acts, while we continue our
own. fgmnetwork (an anti female circumcision page) has this comparison between the two.
FGC Education and Networking Project