You may be right. I mentioned the price increase from the attacker purchasing steem as a mitigating factor in my post. I'm just not so confident that a high-value stakeholder would be unable to disrupt the network if they were willing to burn the value of their investment.
And you're definitely right that if steem takes off enough that people start using it for other purposes, then disruption to the social network might not matter any more. I shouldn't have ignored that point.