Yes, unfair is probably the wrong word - of course it is fair. Unlucky is the word, I suppose, if Verstappen had lost a massive points swing just because of a tyre blowout... so Hamilton's incident cancels out Verstappen's bad luck.
Mercedes are saying it was unlucky for Hamilton, he accidentally flicked a switch that took out his braking ability. Difficult to know how much of this is true and how much is to cover the driver from taking a huge amount of blame. I'm a big fan of Hamilton, it's rare that he makes errors, but whatever the cause, this was a mistake that could have a big impact on the season - going from a potential 25 points to 0 is massive. If we expect Hamilton and Verstappen to be P1 and P2 in whatever order in most races, then this is equivalent to 4 race wins that he's lost by flicking that switch.
Mercedes got a problem during the whole weekend with the temperature of their tires.
After the removal of the DAS banned for this year after the only last year appearance they seem to be in trouble when they need to heat their tires.
This is not the first time they suffer from this, even in Monaco and another GP they needed to run 2 laps to heat their tires in the qualify while the other was ok with only one lap.
They need to solve this problem quickly.