If someone denies the authority of the creeds as man made inventions, that's fine with me. They are man made. I believe they are consistent with Scripture, not equal. However, if someone denies any specific part of the creeds, then I might personally have a problem calling them christian.
Reciting the creed does not bring salvation.
Salvation is by grace, through faith, for works.
The point I'm getting at is that if we look beyond a very very simple definition of what makes a believer, we find that there is far more that separates than may appear. I can't stress enough, because Christ stressed it, that the path is narrow and the road is wide. Is baptism necessary for the forgiveness of sins, do we need to eat the real Flesh and drink the real Blood of Christ to have eternal life? Are we saved by faith alone or are the works we do in cooperation with His will made possible by grace the way?
You see, it's not simply a matter of saying "I believe" there is more and Scripture is confusing (just ask the eunuch) and we do need a guide and that guide is the one visible Church that has the promise of perfection from our Lord Himself. Remember if we are to "take it to the Church" which Church are we to take it to? What body of believers would that be? The Church is visible for a reason.