I feel that this is covered quite well in other threads here, but basically build up a positive reputation as much as possible, outrank negative posts by link building to articles that are the exact opposite (when possible) to negative posts, in time it MIGHT be worth reaching out to negative authors to see if it can be removed (but this is quite risky it seems. Also try to limit the number of clicks to the negative articles during your research, otherwise you will be helping their metrics.