Earlier quoted context omitted.
That may be true, but I'd wager most of the people who are buying into bitcoin for its property as a store of value will be shocked to find out bitcoins other very interesting property. The ease and low cost of transferring those bitcoins to anyone, anywhere in the world. "I can BUY things with these? Wait... I can sell things? I just need to paste a hash?!"
Then one day, some highly motivated attacker will come along and discover the other very interesting property: that the work needed to attack Bitcoin scales linearly with the work needed to use Bitcoin. As soon as a successful attack is announced publicly, faith in Bitcoin will be shaken to badly that nobody will ever want to use anything called "digital cash" for a long time. So the real question you should be askin…
It's worth noting that a 51% attack would only allow double-spending, and it's not something that could be realistically hidden; it would be very obvious what was happening. In addition, the amount of computing power available to the bitcoin network is becoming significant enough that it would be hard to exceed, even with a botnet.
It's also worth pointing out that people still use Paypal, despite all the stories of frozen accounts and people never getting their money back. People also still use credit cards, despite not every instance of fraud resulting in the victims getting their money back.