Humans can indeed be taken apart piece by piece and put back together again. We just don't have that level of technology yet. There's nothing physically stopping it from happening though.
You can melt down a lathe and it is quite hard to reassemble it, and even if you did reform the entire thing people would doubt if it is the same lathe.
Humans have had parts removed and reattached. With transplants components have been replaced entirely. There is a point at which you can destruct a machine from which it is impossible to reconstruct without getting into ship of Theseus issues. That point is different for different things.
Sometimes debating the issue with ai fans is like arguing with children. They come up with all sorts of what they think are "clever comebacks" but really all they do is a reduction to absurdity. It only proves the fact that they are indeed children and fail to understand the topic alltogether. In such scenarios is best to leave them be.
