Put differently and going fast forward; how can you have a mildly inflating currency (eg. EUR) when there's a deflationary currency (eg. BTC) as a viable alternative around?
Would you propose we prohibit crypto currencies? (What would you propose?)
Bitcoin is not an alternative to Euros. That is the whole point. If you switched all euros to bitcoins and asked people to trade those, the economy would collapse as no one would want to trade their bitcoins because mathematically, they increase in value due to the limited issuance of them. Without modest inflation, the economy cannot grow as no one would spend money for investment purposes.
Net (currency-denominated) creditors would.
Net (currency-denominated) debtors would prefer inflation-adjusted currency.
Those whose significant assets and obligations are not currency-denominated (e.g., who own mines or are committed to deliver commodities) don't really care, directly.
Typically, they'd prefer not to hold currency; they'd prefer to make an investment that gives a supra-inflationary return. This is, in general, good for the economy and the society.
"Put differently and going fast forward; how can you have a mildly inflating currency (eg. EUR) when there's a deflationary currency (eg. BTC) as a viable alternative around?"
I dunno, why isn't everyone parking their money in gold?