Believing that what someone else believes is wrong does not by default make what we believe right. We have an unconscious idea that black and white thinking means that if I'm not on one side then I am on the other. We become so caught up in competition of beliefs (evangelism) that we completely fail, or at best largely ignore the issues and problems with our hearts. We have elevated correct information to the level of God and thereby have made it a god that prevents us from knowing God.
We like in constant fear that we may entertain or overlook some piece of wrong information that will cause us to be lost. We believe that we will be judged and saved based mostly on the purity of our doctrines and secondarily on our relationships. In fact, we view many relationships as a threat to our obsession for pure doctrine and so avoid having meaningful connections with anyone whom we perceive or suspect may “corrupt” our accomplishment of “truth-gathering” up to this point in our lives. This has the growing tendency to cause us to associate more and more exclusively with only those who most nearly agree with our viewpoints and we more and more shun and pull away from everyone who makes us religiously or intellectually uncomfortable.
Evangelism as we see it today is largely an attempt to forcefully persuade people in a short time to align their intellectual/religious beliefs and external behaviors to be very close to ours so we will then have more people we can feel safe to fellowship with. If we can convince them to change with enough proof texts and arguments to switch sides from outside our church to inside our church then we suppose they are now converted and secure. From then on they only need weekly doctrinal maintenance and updating through unifying lesson quarterlies and formal sermonizing. Fellowship is considered a perk or maybe even a necessity, but only as a means of support for doctrinal growth and settling.
This is the model and reasoning developed and practiced by the Jews in Jesus' day and further fine-tuned and perfected by the Holy Roman Catholic Church for centuries. And as much as conservative protestants despise the Catholics they are, in fact, following very closely their lead and beliefs in how to correctly arrive at “truth” and “salvation”. If the truth were really exposed, it might be discovered that our animosity toward Catholics is rooted deeply in jealousy at their successful control over so many minds creating overwhelming competition for us in our desire to control other people's minds. Our doctrines may be different but our spirit and methods may be very similar. Jesus says to us as forcefully as to His own closest disciples, “You do not know what kind of spirit you are of...” Luke 9:55.