The rules are reversed for Mohammed though. The fact he owned and sold slaves is excusable because it was a different time

Not just Mohammed. Jewish slave merchants are routinely excused in the Jewish press because they were simply participating in a common practice of the time. If true, why does this excuse not count for whites that participated in the slave trade? Why do only Jews get this pass?

Particularly given the leading role of Jews in the Dutch and Portuguese slave trade. There were open Jews, but many of them were also Marranos, crypto-converso Jews.