What Would You Do? Evangelise or Let'm Die?

I read over and over how it’s wrong to be evangelical in one’s beliefs. But everybody does it. "Oh man, you’ve got to see that movie." "You should stop eating meat!" "I think that people should take the bus instead of using their cars." "You should just accept that homosexuality is as normal as heterosexuality." "You should stop smoking cigarettes." You should try smoking pot." "Vote for this person and not for that person." And on and on it goes. People feel strongly about these issues and have no qualms voicing their opinions. Since I believe the claims of Jesus, why can’t I present what He taught without being thought of as doing something wrong? And while we're at it, ask yourself why listening to the case for Jesus feels like pressure and / or offensive while hearing about Buddha or Native Spirituality or anything else feels sophisticated. Regardless of that, here’s what I think is going on.
Let’s say there is a pond on my property. And let’s say that we’ve had a few really cold nights. While there is ice on the pond, it isn’t very thick. Along comes a guy and his little boy. They’re carrying skates and are heading toward my pond. I yell out to them that they shouldn’t even think of skating because the ice isn’t thick enough. The guy tells me, "This is my life and I’m free to do what I want to do. And for what it’s worth, I happen to believe that the ice is thick enough. So quit trying to shove your beliefs down my throat!"
"Yes, I understand that it’s your life" I reply. "But I know that the ice isn’t thick enough. You’ll fall through and drown."
Now I ask you. If I continue to caution him, am I being insensitive to his beliefs? If I put a hand on his shoulder and try to stop him, am I being narrow minded? After all, he's as certain that the ice is fine as I am certain that the ice is too thin. If I let him go and do what he believes is best, am I being this really cool open-minded free-thinker? Which course of action means that I love the person more?
You see, I believe with all my heart that Jesus is trustworthy and what He teaches needs to be taken seriously; more seriously than anything else in the world. So what should I and other Christians do? We believe that if you don’t heed Jesus’ warning, you are going to fall through the ice so to speak. What would you do if you were in my place?