Here, everyone thinks that Bitcoin cannot be changed, consensus and all that crap.

But you've already seen that Bitcoin can be changed, whether it's because of a bug like the Sewgit witness and that bug wasn't fixed, or changes made by a dominant implementation like Bitcoin Core in op_return.

Gold cannot be transmuted, it's physics, but Bitcoin is a p2p network and it's software, and software can be changed, and there are social tactics to deceive people so that there is no real consensus, as is currently the case with an implementation that accounts for 78% of the network.

You have to defend Bitcoin, and you have to get this into your head: Bitcoin doesn't defend itself just because some people say so.