I see, so to be clear, it's the concept or idea you want people to accept - am I correct? I can't see why that would be a problem for many people to be honest, though there maybe others who simply cannot conceive of it. I dont understand why folks would react so energetically to the simple concept, perhaps there is more to it than that? Maybe they think you have a different objective than simply having the idea accepted as valid?
The reason I was so specific about the question was that you seemed to me to be also insisting people accept more than just the concept eg referring to what God has done without qualification (ie assuming he/she/it exists etc). :)
If you want others to go further and ask people to accept the possibility in the general sense, then I suspect that wouldn't attract massive opposition. However the next step is trickier - probability. Then we are in the territory of evidence, not concept. I suspect that's where the real arguments begin. You may have sufficient personal evidence to convince you that there is a heaven and eternity but that won't necessarily have any affect on another person's assessment of the probability of it being correct, ie heaven and eternity.
I'm not sure how calling something a lie means that makes believers liars, though it is perjorative. If the concept of heaven and eternity is not true then it is false yes? In that sense it would be perpetuating a lie or falsehood. That doesn't necessarily make believers liars, it may simply mean they have been taken in by it. If however folks are teaching such things and don't believe them, or are not being honest about the evidence, then they are being deceptive, ie lying aren't they? Maybe it would be better to say it is plain wrong rather than a lie.
For me, adopting a position of certainty at either end of the debate doesn't really help. Obviously if one has direct revelation of the existence of heaven and eternity, that's nice but unless it can be shown to be anything other than some form of delusion or an invention it isn't worth much to someone who hasn't experienced it (as per the Paine comment earlier). The moment one tells others about it and insist it true, it is going to be challenged though isn't it?
To me it does seem there are many strands of evidence suggesting survival. On their own they are often open to refutation, even if only by that old saw "fraud". Taken overall they do weave a stronger thread though.
* off to bed :)