I wouldn't phrase it as a declarative ("Not everyone can be convinced!"), but as an agnostic position ("I don't know if everyone can be convinced."). And it's just my thought; I'm not promoting it as God's position. Neither do I see it as something static in time - that people are born inconvincible. Rather, it's a hardening over time.
Ok. Thank you for clarification on the first part.
Hence, let's frame it in a less certain and more of a hypothetical manner of a loose analogy of what you seem to be implying.
Let's say that a huge percentage of people would gradually go blind over time (which actually does happen). Would it be reasonable to expect these people to see signs on the street? Wouldn't it be more reasonable to modify our general expectations in scope of ability of these people, and shift from vision to auditory clues or touch?
You seemed to answer all of the prior questions in the affirmative. God wants to us to believe that he exists. Such desire seemed to be phrased in terms of general expectation for every human being when it comes to some moral standards.
YET, he doesn't seem to be willing to take the extra step to modify his revelation to what any given person is able to believe. Hence, you invite me to talk about Baptism with a Lutheran pastor when it likely not going to resolve the issue at all.
So, we have a couple options .
1) Ether people are wrong about God's expectations, and God doesn't really care about whether we believe or not (you ruled that one out)
2) Or God expects and wants us to believe based on the evidence that not able to convince us (Which I'd like to discuss as to how that works)
3) Or it's seemingly a projection of people who believe certain things and attribute it to some supernatural agency to derive certain meaning for what they are doing, hence the evidence revolves around those things and not in any conclusive evidence that would convince us.
4) I didn't want to be biased, so I'd like to inject a possibility that would work for you - there may be some unknown reason as to why such expectation is the case.
Hence, I wouldn't be quite like Fuminous in that regard. Given my history, I'd probably take a lot softer approach. I think we can continually deny everything and anything to the point of hard solipsism, but that's not the general mode of my personal discussion. If I ask a Christian God to demonstrate its existence, and all of a sudden I get the "Moses burning bush" experience. I'd think it generate enough dissonance in my worldview in order for me to investigate and pursue it further, and take religious claims a bit less dismissively. In the very least from a position that "It happened to me too".
But, that's not the case. What we get instead is an educational and indoctrination experience that goes about anchoring our emotional states with some ritualistic observance, and it's a rather bizarre way to come to know someone personally.
For example, if I have never met my father, and I get a note:
"Drive up at 12:00 am sharp in the middle of the cemetery. Make sure that you wear nothing but speedos. Cut off the head of the chicken, and smear its blood all over you... and then you will meet me. I know it sounds weird, but all of those things have a lesson for you to learn about my love. But, most importantly, you will then meet me, your father!"
Why would I take the above with anything else than a skeptical approach? Can I be blamed for ignoring the message and not doing those things? If someone does care to show me that they exist, and they'd like to have a relationship, I think that the prerequisite rituals seem excessive, especially if these rituals are not performed in context of a culture we can relate to, and thus it becomes a rather bizarre and questionable endeavor.
But, let's say that I was curious enough to drive up to the cemetery at 12am. Would the fact that I wasn't wearing speedos and smearing chicken all over my body translated as "lack of faith"? And would the fact that I didn't wear the "brand-name" speedos, and took it a more generic understanding of the word "speedos" matter to my father as opposed to my willingness to drive up and meet?
So, the question remains, why not convince people in a way that they can be convinced individually?