Well, is it a sin to worship and fellowship with Non-Catholic Christians? For instance, I am involved in a college ministry (called Christian Campus House) that is a non-denominational ministry (the college minister is part of the Independent Christian Church/Church of Christ movement), but people of various denominations (including Assemblies of God, Anglican, etc.) are involved and, actually, I met my current RCIA sponsor at CCH.
Anyway, I hang out there a lot (they have a student lounge, etc.) and I go to their Tuesday night thing called M&M (Meal and a Message), where there is free food, then worship (some people take Communion; obviously, I do not) and a message (obviously, the messages are not geared for Catholics, but I feel I am pretty good at knowing what is in line with Catholicism and what is not…nothing Anti-Catholic though that I have heard). Then, on Thursday nights, they have ‘Man Church’ (it’s basically a bunch of the guys get together and hang out, maybe do a service project or something or discuss Scripture), which I also attend.
So, is this sinful to be involved with them? Obviously, I always go to Mass on Sunday.
Also, is it wrong to fellowship with non-Catholic Christians (after all, I still have many friends from my Protestant days)?