The nice thing about dampening collusive votes in code is that we don't have to sit around in threads like this arguing about the "ethics" of voting and searching our souls. The nice thing about having a benevolent dictator behind the site is that we can just have things like this fixed automatically.
The ethics of voting are not my focus. My concern is the potential collateral damage of the "punishment." Google has had to take similar actions with its algorithms and even their best efforts yield collateral damage - I suspect this is why it takes them so many people and so much time to make improvements.
The voting system on Hacker News is small beans compared to Google rankings (which can make or break entire businesses), but it doesn't negate the validity of showing concern for a site from which I get much of my daily reading material.
I suggest: stop worrying, vote however you want.