interrogative + も polarity
grammar3 sentences
The pattern [interrogative]+も flips its quantification depending on the predicate: with an affirmative verb it gives a universal positive ('everyone, anyone, anywhere'), with a negative verb it gives a universal negation ('nobody, nothing, nowhere'). 誰にも親切 = 'kind to everyone'; 誰にも親切ではない = 'kind to no one.'