Answer:
You are assuming that only religionists are moral. You need to expand your thinking because your friend's morals may be better than yours.
Start your analysis with Eastern religions that are not theistic and yet are deeply concerned with how to be a good human being. There are many philosophies that teach that moral actions are only those that produce good results and that as humans we should all strive for a good result for our actions. In fact, the strongest moral behavior can come from individuals who believe they should be good simply because it is right and benefits society.
Many religionists are good because they fear punishment or the denial of a heaven in the afterlife. Atheists may have stronger moral tendencies since they are good simply because it is right to be good. Atheists engage in good ethical and moral behavior as much as any other person does . . . perhaps even more since they don't usually discriminate against other groups. They take the unique responsibility for their own destiny, actions and decisions. They seek answers in science and philosophy and thus are not prone to false prophets who preach a destructive message. Remember that militant religious extremists justify terrible actions by using their religious beliefs. They have no good moral foundations.
Religionists have for thousands of years tried to portray the non-religious as evil and devoid of morals. If you were paying attention, you would have noticed all the religionists who have made current news doing very bad things in the past few years. That serves to prove that good moral behavior does not require religion as a guide. Our knowledge of right and wrong is innate. You should try to be good all on your own. You can start by not persecuting your atheist friend because she/he doesn't share your particular, and possibly peculiar, beliefs.
The bottom line is that you can trust your friend to the same degree you can trust anyone else and stop persecuting him for not having your religious beliefs.