That's the definition of fungibility.
BlackHat, I understand how strong and enthusiastic you may have become and, to be very honest - I'm not against it frfr

To a point that It's almost impossible to convince you otherwise (which isn't my motive)... Ehnnn, but the sad part is that the truth can't be diverted for your interest sake.
Bitcoin has all the criterias to be called a "fungible coin" - ofcourse the value of 1/4, 1/5 of 1 BTC still equals the wholesome coin
[This is the base and your own very perspective of understanding fungibility]... The transparency of the blockchain has slowly been made a target...Do you not believe just as they've proven that - atleast 38 - 46% of Bitcoin transactions(on the blockchain) are "tainted coins"? And that most of these coins don't get redeemed at the same price tag? Look, I don't have anything against Bitcoin itself - but I can't vouch that peeps are patronizing them mixers for nothing sake!