I have to disagree. What has happened with the Ethers, ETH/ETC has nothing to do with the situation in Bitcoin. Bitcoin has successfully hard forked on one or more occasion and may well do so in the future. The reason there has not been a hard fork in Bitcoin over the blocksize issue is that nobody has proposed a real solution to the blocksize scaling issue that actually works over the long term. Without such a solution the necessary consensus in the Bitcoin community is simply not there.

What makes the Ethereum hard fork different and a very dangerous precedent is that this hard fork was not about significantly improving Ethereum or about fixing a vulnerability in the Ethereum code. These are situations where immutability of coin ownership on the blockchain is preserved, It was about reversing a particular set of transactions. The prevention of this kind of transaction censorship is why Bitcoin was invented in the first place. If one reads Satoshi's original Bitcoin paper https://bitcoin.org/bitcoin.pdf this becomes readily apparent.

What Vitalik has done here is actually prove Satoshi wrong, since a highly distributed Proof of Work blockchain is not enough to prevent this kind of attack. This attack worked because it used persuasion rather than force. It relies on manufacturing a clearly identified  enemy and then persuading the majority that attacking this enemy is in the majority's best interest. History has many examples where this approach has led to war, genocide etc. A critical component of this attack is that the majority must be able to clearly identify the enemy and then launch the targeted attack.

ETC is just as vulnerable here as the pre fork ETH. Consider for example if the enemy was a "really evil" bank that had just been bailed out by the taxpayers at great expense. In that respect so is Bitcoin and any in the clear blockchain, including Litecoin for example. One solution worth considering here is to blind the censor by using an anonymous blockchain. For example it is next to impossible to pull of this kind on attack in Monero, in spite of the fact that Monero has hard forked in the past and is scheduled to hard fork in the future. What the Ethereum hard fork has done here is make the case for anon coins much stronger.  

Edit: The answer here is not to prevent a hard fork, it is instead to prevent a hard fork that only targets specific transactions.