This question already has an answer here:
In an paper, an author cites my article in which he states that I said "something" and that it is wrong. Not only have I never said "something", but the article he cites is about a completely different topic (there is no ambiguity about that).
Obviously the reviewers have not done their job appropriately, but that it too late. Worth mentioning I suspect this is due to my non-responding to his solicitations, but that is not the point here (see edit).
How should I react (ethically) to that?
This question was marked as a duplicate but I will add a few clarifications out of respect for the commenters/answerers: I did not expand too much on the solicitations because I did not find it very relevant. What happened is that I was approach by a researcher who wanted to extend his research topic to mine (or more generally to that of the company I'm working for). He invited me to contribute to some funding project, which I did, then asked me some technical questions, to which I answered, up to a point where I got annoyed by him not reading the references I suggested. He basically wanted me to spoonfeed him everything. He then cited my article in a negative manner, including a completely false statement (that I said in my article that a solver had property X when the cited article does not even mention anything related to a solver -- and it's not just citing the wrong article: I never wrote anything related to this wrong statement).