Do they get that inflation destroys savings
The Keynesians' programmed response is that it's good to destroy savings because that motivates people to spend and invest.
and that it's a stealth taxation?
For non-libertarians that doesn't sound scarier than stealth road maintenance.
And really, this is a moral issue that's very intuitive.
No it isn't. If you own a house, does building new houses violate your property rights? No. If you own a gold bar, does mining gold violate your property rights? No. Expropriation and devaluation are different things. Property rights can protect you from the former but not the latter.
Do they understand that it's decentralized?
They do and for them that's a bad thing because it means their best friend the government can't properly punish scammers and other criminals.
That it's digital and that digital things can have value?
Sure: bank accounts are digital and valuable. But what gives them value? They will probably say that it's the government. Also they might point out that everybody can make a new cryptocurrency which should reduce the value of every specific cryptocurrency. If at that point you answer with "Bitcoin is not a cryptocurrency" then you've lost already.