@OP.

My husband and I are very devout Christians.  My husband is even a Biblical scholar.  He enjoys reading the Bible in Greek just to make sure he is understanding it correctly.  I met him at a Christian college.  I am even going on a mission trip to India in a few weeks to work with an organization called Harvest India.  I am also well known on this forum as being a very vocal Christian. All that said, I am very for Bitcoin.

Sure there are people involved that are not Christian.  We are "in the world not of the world" right?  And yes, I think that Bitcoin could certainly be the "one world currency" that is talked about in the Bible (all the more proof of it's success).  However, in scripture it is not the "one world currency" that is evil.  It is the control of the people by putting a mark on hands to buy and sell by the antichrist, whoever that ends up being (perhaps Satoshi if at some point he comes out of hiding to "save" the world from fianacial ruin?) that is the problem.  I believe it is incredibly important that Christians purchase as much Bitcoin as they possibly can.  Bitcoin is not owned by any government and it is peer-to-peer and it just might give Christians the flexibility needed to make choices when the day comes that we are being told we have to have a mark to buy and sell.  Having some coins that are not within reach of governments might be the only thing we can access before being put to death or in jail.  Just something to think about.

It kind of reminds me of how so many Christians were against movies when Hollywood started out.  If anything, it would have so much better if Christians had just embraced movies and came out with more wholesome movies at that point.  Instead they feared it and because of that the industry has now swayed generations of people in less wholesome directions.  

We need to be "cunning as serpents and innocent as doves."  Using Bitcoin for God's purpose is where my heart is at and I would encourage your uncle to at least pray about it more seriously and read him my comments as well.

Edit:  As for your uncle's concern of Bitcoin's early adopters having some deep rooted connections with transhumanism and having extroprian roots, this just seems to be the pride that comes with most people I encounter that are drunk in their own intelligence and is just typical of the scientific community today.  I had a biology teacher that had me read Adolf Huxley's Brave New World in high school. (this was 20 years ago)  I read the book and thought it was completely ridiculous and a fantasy at best.  I was shocked to learn that he seriously believed that it was a brilliant look into what the future should be, but it was a cold and loveless world in my eyes.  This was my first insight into how the "intelligent" minds perceive things.  Now I see people that think they know more than God.  They don't need God and they even want to find a way to "outsmart" God if that was even possible (but of course they don't even believe God exists anyways.)  So the cryogenics and transhumanism is just an extension of this sort of thought.  Perhaps they are the early Bitcoin developers because they are highly intelligent?  The more intelligent minds are drawn to these sorts of things?  I am not entirely sure.  It doesn't mean that Bitcoin isn't brilliant though and a intelligently designed work (designed by those whom God gave the intelligence to begin with )