Suppose last week I told you, "Oreos are the only black and white cookie upon the face of the whole earth, with which I am well pleased".
The same goes for white cookies.
In fact, we run into a similar problem when we claim Oreos are the only black and white cookie. Hydrox claims to be the first creme-filled cookie and there are other Oreo knock-offs which are no less black and white than your typical Oreo.
If the reducing our statement about cookies to "Oreos are the only black cookie" is inaccurate, could it be that the "only true church" reduction is no less problematic? The more I learn about other faiths, the more I recognize the truths within them. I have no trouble saying both the other churches are true AND declaring the Church is the only true and living church of which the Lord is well pleased.