Permissibility of listening to moulana anwar aw lakis lectures

asalaamu Alaikum mufti saab
i wanted to know if its safe to listen to Imam Anwar al awlaki lectures? below are site where u can get copies of his lectures an books and information on him wiki pedia not 100% but +/- correct
http://www.salaattime.com/anwar.html
http://en.wikipedia.org/wiki/Anwar_al-
by the way i also listen to mufti saabs lectures but some times like a different voice as well
JazakAllah