He was trying to blame the Prophet Muhammad for doing what was normal and customary for his time whereas in many states in America, the age of consent was as low as 7 years old. Take a look:
Age of consent:
City ……………….. 1880 ……… 1920 ….. 2007
Delaware ………… 7 …………… 16 ………… 16
Alabama ……….. 10 ………….. 16 ………… 16
Arkansas ………. 10 …………… 16 ………… 16
California ……… 10 …………… 18 ………… 18
Colorado ………..10 ……………. 18 ………… 15
Connecticut …. 10 ……………. 16 ………… 16
Florida ………… 10 ……………. 18 ………… 18
Georgia ………. 10 …………… 14 ………….. 16
Idaho …………. 10 …………… 18 ………….. 18