Owuor is in good company, every church condemns witch-craft in no uncertain terms. They also condemn a visit to the sangoma (mganga). They dont seem to care about wife inheritence all that much.
Also, witch-craft and widow inheritence are not at par. I am surprised you're comparing them so matter-of-factly as if they go together/are equal. For one, only one of those has received a divine sanction at least at on point in History.
Reading around the net on it, I don't see what was so different between what God commanded Jews and what Luos (and many Africans) commanded their men. He basically asked them to sire kids for the dead Jew, have sex with the widow. Neither did he give the widow an option of opting out. It was the brother that could opt out. After that, she could marry someone else, but not before. In the African context, the inheritence is the shamba. The children inherit the deceased's property ( their "dad") but not the brother's property, while in the Jewish context, the brother takes the whole of the deceased's inheritence and takes care of the kids he sires for him with it. Either way, the aim and means seems to be the same. The only difference seems to be the Jewish property system compared to the African communal property system. But most of all, I am not convinced it is as prevalent as may be believed. Just seems like another African cultural practice that is on its death-bed like all others (including polygamy).
If heavy cultural pressure is bad, I think that goes for male circumcision as well. After all, sex is not harmful, but we dont want people being pressured into it. It cannot be right for men to have absolutely no choice in today's social context regarding whethertheir foreskins stay. That is, if the undue social pressure for people to do things is really the big concern.