I read the relevant sections of the USCCB-commissioned report, and I do not draw the same conclusions as Kirby and Robertson, i.e. I do not feel that it clearly supports the notion that Catholic priests are more likely to be abusers than the general population. Am I misreading it? If so, could someone point me to specific passages?

Note that I am not by any means trying to be an apologist here! While it is unclear to me that Catholic priests are more likely to be sex offenders, I feel the data is fairly clear that the victims-per-offender is much higher for Catholic priests, exactly because of the cover-up and the shifting from parish to parish. Even if the problem of abuse in the Catholic clergy is no worse than what is experienced in any similarly-sized institution, the institutional response has been tragic.