When you say your church is "the only true church", many will indeed see that as an attack on their Faith and/or church. This is a sleight-of-hand the Mormons have become quite adept at. They insist that THEY are the "one true church" and when people make the case that this can't possibly be true, they complain "Why are you attacking us? We aren't attacking you!"
When a church claims to be "the one true church" they had better not be surprised when others put that claim to test.
That's why we should only put our faith in G-d, not the church with is run by fallible men. We should let the Holy Spirit guide us in our faith. The Holy Spirit is a teacher, comforter and guide.