One troubling aspect of the idea of one true church out of all the many in history is the requirement that this true church exist in all ages of human history since Christ. The true church is the supposedly sole disseminator of the knowledge required to achieve a personal salvation; so, if it ever ceased to exist, then there would be a zero chance that men could be saved. The Catholic Church recognizes this fact and claims a historical lineage all the way back to Peter. Protestants, on the other hand, normally trace the existence of their particular brand of Christianity back only to the Reformation which occurred centuries after Christ and the existence of the Catholic Church.
For those who adhere to the existence of a true church other than the Catholic, this represents a tragic situation. By their reckoning, for a vast portion of history since Christ, no one could have been saved because no one was teaching the right process or doctrine. Some may want to assume that the true church has always existed in small, unrecorded groups, but given the fact that Bibles were not even available to those outside the institutional church of that day, one must wonder how these small groups even knew how to establish this true church.
Salvation by church disseminated knowledge just does not work, unless God never intended to provide even the slim chance of salvation to most of humanity. Some may want to characterize God in that way, but I cannot.