I can see gunpoint robbery (like an updated IRS agent when not paying your taxes, or other criminal, to get the flavors down to two)

And my full nodes helps me to NOT inform the potential robber listening online with his node connecting me to my payments.

But how does my full node prevent fiat inflation?

My node is not connected to any fiat system inflating the fiat money supply. Even in a roundabout way where you could say without nodes there would be no bitcoin network, it does not prevent anything from happening outside the network...