I'm not entirely sure about that... Of course, downvoting provides some sort of a way to fight against people who have less SP than you, but people with a lot of Steem Power can retaliate on you with so much harder downvotes that you will suffer harder than they will.

If he is, as you say, well-known, then chances are that he also got a lot of Steem Power, which makes him essentially invincible on here as well. If you downvote him, there's a high probability that he would do the same to you and perhaps harder as well.

I've downvoted bad people in the past and got downvoted much harder for doing so. The world isn't a very fair place and I'm not sure if Steem really changes that.

You acted well in the situation though.