Smart users should not only vote but also retaliate with downvotes when their friends are downvoted

Depends how much you want to lose for yourself, because some of the malicous downvoters take this counter-downvotes as a personal attack and start downvoting too.
I usually don´t want to get involved in any downvoting war - with a few exceptions. This whole thing went way to far. Unfortunately there is no governance controlling that downvotes are justified (and only fight spam & plagiarism).