How to deal with an aggressive fanatic friend who claims to be an " atheist secular"?

i have this friend who used 2 be very religious for a long time and suddenly after reading some books on secularism, he claims to be a secular and sometimes atheist. Yet! when i criticize the power of some churches on naive people, he gets really angry, his hands are shaken, he swears and gives me terrible accusations:( and i don't wanna loose this friend PS: i am not Christian