Humanity pursues truth.
Let me rephrase that, humanity pursues what it thinks is true and has no way or means of truly knowing if the ideology or belief system they've found is true (as compared to God, who is ultimate truth, bear with me here). This is one level (Postmodernism). If it works for them and if their conscience isn't bothered then it's good enough. Of course this is subjective. If someone's conscience is less sensitive than the other person's then you're bound to encounter hard feelings and misunderstandings. Okay, apologize, move on. Maybe you'll learn from this and even make an acquaintance.
Consider the exhortations of people—religious and non—who are on fire about whatever it is that they're passionate about. They found the truth and now they want you to know—and convert. But do they care about you? Really care? Why are they telling you how they came to find the(ir) truth, wherever it happened to be? What's their motive? Look in their eyes. Anyone not willing to be a friend first is not worth listening to, I say. Make a friend.
Here's what I believe: Jesus is the Truth. However, I also believe that people are smart. (these statements are not mutually exclusive). They listen to what you've said. "Doth not the ear try words?" (Job 12:11) and if you (a professing Christian) are not right with God, then the Holy Spirit—The Spirit of Truth—most likely will not be released to back up your words and witness to their heart what you've said.
This is why it's imperative that we as Christians keep our hearts transparent before the Lord, our sins under His blood and our testimony pure. Jesus says that the pure in heart will see God (Matthew 5:8). Then when we talk to people about the Jesus we know, they'll see through us (in a good way) to Jesus. See also Luke 16:8.