u/1r0n_m6n

I'm looking for the title and author of a sci-fi book in which mankind encounters aliens while our planet is torn by wars, close to its destruction. At the end of the book, the hero meets the aliens to discuss the situation and they offer to help bringing peace by making humans so dumb they'll no longer know how to use their weapons. The hero being the only human in contact with the aliens, it's up to him to decide whether he accepts the offer in the name of humankind.

The style reminds me of Arthur C. Clarke, or possibly Clifford D. Simak, but I haven't been able to find a book matching this description so far. Any idea?