How can i explain this to my mom without starting a fight...?

Well as far as i know.. my mom is very religious about being catholic and such. For me... i don't really believe in such but in some ways yes. I honestly think in my opinion we can all live a good life without ever stepping into a church or so and have good morals and knowing things from right to wrong (even then outside of things such as... playing violent games leading to a bad life...to which it doesn't as i do too but i dont act like that in such ways. I would want and wish to explain it to my mom that i don't believe their views but at the same time i really fear that she will retaliate bad enough and just putting me down saying that im saying it just because i wanted to stay home and play games all day. That may be logically true but im just only expressing my opinion and it feels like i CAN'T express ANY opinion at all... or even then i don't have rights. Yeah i know some of you people will say "well you live on their roof...live by it"...what im trying to say, its just that i don't want to start a huge fight between me and my mom just because im expressing my opinion and thoughts about it and not threatening it in any way shape or form and i respect her views and just leave it at that. So is there a way to go around it or just...go with the flow?