52% of 70% of the voting population said "No".
The argument could be made that the 30% that did not vote deserve what they have coming for not bothering to take part in such a monumental national decision. Not voting means "I don't care", so you let other people decide and then you live with the consequences.
Isn't that the point, though? UK just said "no" to half a century of following these principles - making sure there are consequences means protecting EU ideals, not harming them.
Sure, in practice there will be plenty of replacement treaties - but for EU _and_ for those principles it's quite ok if UK ends up 6th or 7th economy instead of 5th. We're not talking about bankrupting anybody here.