That excuse doesn't work when bitcoin launched with higher than 1MB blocks in the first place so a "bitcoin can never fork" purist doesn't even have a valid reference point to stand on.  The fact is, just about everything regarding bitcoin (and every other cryptocurrency) is completely arbitrary in nature and wide open to rough consensus attack.  There are TWO ethereums.  There could be 100 ethereums tomorrow.  It's pretty much inevitable there will be more than one bitcoin.

This is why it's called a cryptocurrency and not money.  Currencies are arbitrary games that people create, while money does not fork or change.  I don't have to worry about Adam sneaking into my house and trying to fork my gold or silver.  Nobody should even own currency in the first place unless you actively use it or are a forex trader.  90% of this forum are basically acting as forex traders without the skills to do so.  It's also far more common for people holding currencies pretending they're stores of value to get horrifically burned than to profit.