Also remember that this isn't the first time this idea of 'lets rollback a blockchain due to a hack/attack' has been floated or even tried. The first major blockchain rollback almost completely destroyed the cryptocurrency [1]. Since then, some major hacks have happened and the community/developers rejected the idea of a rollback [2][3]. That was a hard lesson, and hopefully the current developers will learn from the short history.

Also to your point, yes, Ethereum is not as decentralized as some would like to claim, either from a stakeholder perspective, or from a mining perspective, or even from a 'who holds the power' perspective. I suspect that's what makes it so efficient though, in terms of changing protocol, or making decisions on behalf of stakeholders.

[1] http://247cryptonews.com/vericoin-lack-integrity-bailout-min...

[2] https://www.cryptocoinsnews.com/official-nxt-decision-blockc...

[3] http://www.newsbtc.com/2014/12/17/opal-recovers-1-7-million-...