I don't think anyone here is suggesting Original Sin is an evangelistic (or pastoral) tool. But it
is fundamental to developing a coherent, systematic doctrine. Some may say that's a bad thing. Personally, I think any N (especially) will grope towards it, since doctrine is organic. You can't believe one thing without that affecting something else (and so on and so on). So whenever issues like original sin, freewill and predestination are discussed, and someone inevitably jumps in saying it's unproductive or even counterproductive, I get a bit annoyed (in my INFP way). I can see where they're coming from, but we're not preaching the gospel to people who don't know anything about Christianity here. Not intentionally, at least. We're discussing doctrine. I would think that INTPs would be all in favour of being systematic in their doctrine. I think original sin is an extremely beneficial topic to have a good understanding of if your Christian worldview is to have a strong and/or consistent foundation. Even if that understanding is to reject it totally.
As for Jesus' emphasis, they were different times back then. Different battles that needed to be fought. If he were to walk the earth now, I'm not at all sure that his focus would communicate itself in the same way. That's not to say that he would give lectures on original sin to the 5000. But I think he may have added a few things at different stages. And who's to say he didn't?
Right now with humanism in the ascendant (in the West, at least), it's pretty bloody hard to talk to anyone about Christianity before the assertion of inherent human sinfulness is called into question. The essential goodness (or neutrality at least) of people vs the essential sinfulness of people. Do "good" people who aren't Christians go to hell? What about my dad, who was a good bloke but not religious? If you aren't certain of the fundamentals, your reply is basically going to be "I don't know, but hey: God's pretty cool! I'm sure he has it all worked out." I guess that's good enough for a lot of people, but I for one can't live with that sort of uncertainty on such fundamental issues. Maybe it's the Fi. Original sin, predestination, election of the saints, the nature of freewill; these are all things which need to be addressed and resolved imo.
Here's a small tangent, hence the small print: As far as a practical mechanism, the notion of sin being transferred in this style is one reason I broke from those beliefs because of the destructive resonance -- the outcome is bad. (At core, it creates a feeling like this: "Your heart sucks just because you're human, in fact God can't stand you in his presence because of your suckiness, and so you're damned to not be allowed near him ; but He loves you despite how sucky you are and is so kind and gracious that he'd like to save you if you just let him somehow." It's a "shame" mechanism at core, even if it allows a possible good in that you might think someone be kind enough to "love you anyway" -- gee, that makes it better. I could never treat my kids that way, I see it as destructive, not healthy.)
I hear where you're coming from, I guess. Or I think I do. But what's the alternative? "You're AWESOME! God thinks you're RAD! He thinks you're so cool and wants you to accept his love because it would make him really really really happy! Don't worry about the sin stuff because it doesn't really matter and you can work on that a bit later"? Okay, so the sarcasm was cheap, but I dunno, I don't see that in the bible. I think people think Jesus was way more
tolerant than he actually gave any indications of being.
I dunno, maybe I've misunderstood your position. I'm pretty sure you're more widely read in Christian literature than I am. Which may mean something, or may not. I dunno.
And I can't believe you would slip all that in on an edit. Tsk. Tsk. Again I say: tsk!