That’s assuming that a direct attack on a network is the only option. What I described was much easier: if the government requires payment of taxes or reporting real identities, you’re going to have trouble exchanging into real currency unless you’re paying enough for someone to risk money laundering charges. Similarly, if a commercial exchange is required to refuse transactions traced to an address on a list, it’ll effectively limit their ability to use the network. Most companies aren’t going to risk their business on those transactions even if they’re technically capable of processing them.

Since the blockchain is public all of that can be retroactive, too, so any transaction has the risk that the other party will leak your identity, which similarly disincentivizes other people from taking them.