Slightly unrelated to the point made above, but there is one particular weird argument that always seems to come up (at least in my circle of friends and acquaintances) when talking about immortality.

I tell someone plan to live forever, and the response is "Not me! That must be terrible! Imagine being forced to watch as everybody you know dies. And what if humanity dies out? You'll be sitting on a barren world for all eternity. Imagine how bored you will get."

I call this the 'cursed with immortality' argument. It is of course utterly ridiculous, but it's surprisingly common. My guess is that people place the idea of 'immortality' firmly in the realm of fairy tales, and in fairy tales the immortal being desperately trying to die is of course a common theme.

People who use this argument aren't stupid. They of course realize that an immortality curse is the stuff of fairy tales, and has nothing to do with science. But that's the point, they don't consider the question to be part of the realm of science.

And so if you ask people about immortality, make sure they take the question seriously first, and consider it in the right context, before assigning any value to their answer.