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I have no chance against him, because I don't have big voting power. I has 100 times more steem power than I have.
If I downvote his posting, he loose maybe 1 cent, if he downvote my posting, my posting will probably blocked from steemit and nobody can see it anymore.
Steem development should fix that, but they don't care.

I flagged him and his rating dropped 10 points. If more people fight back his power will diminish. Don't let him get away with it.