Bitcoin is a system that is woefully misunderstood by many people. It is not a honey badger. It is at heart a system that takes a positive view on humanity. It's a system built on the assumption that the majority of players are honest and stick to the rules. In a world in which most people think long term and don't spend all their time trying to stab each other in the back, this works.
But is humanity really that way? Or does society require a small number of rulers keeping the ruled in line? Every day that Bitcoin works well, the answer shifts towards "no, decentralisation of power can work". And if BitUndo gathers significant hash power, the answer shifts more towards "yes, decentralised solutions can't work if they rely on an honest majority".
If you read the literature, distributed systems very commonly require some kind of honest majority, if only because the definition of "honest" needs to be set by something. There isn't really a way to make Bitcoin work in a world where most other players are colluding against you.