I think that part of the problem is that religious belief or philosophy is an intensely personal experience. It is rather like debating love. I think that many people may tend to go to the explanation after, not before, the feeling sets in. We believe something and then we set out to prove it. Which is kind of like trying to rationalize love.
If it is your intent to help your friends by sharing Buddhism with them, then that can be a good thing. But if it is your intention to prove to them that you are right, with a capital R and that they are wrong with a capital W, then what is the point? It is not helpful to them. It is merely indulging your personal desire to prove that you know best. Would it not perhaps be better for you to show them, with your own experience, how Buddhism is beneficial to you and perhaps may be to them also?
Religious belief is not right or wrong. I may believe that Buddhism is a very good thing because the focus is to alleviate suffering. Buddhism teaches us, through its practices, how to alleviate that suffering, thereby making our existence less painful. If we decide to engage others about their beliefs in order that we can show the superiority of our beliefs, how is that helpful and how does that help to alleviate anyone's suffering? Is that not merely about 'winning'? I know that when we are young, winning is important. Being right is important. Other's acknowledging that we are right is even more important. But helpful?