This is an obvious factor for most of the SEOs. Google AdWords has a way of excluding a website for entering the search results for particular keywords, while the organic search results for Google does not do that. One cannot instruct Google to not rank websites when people put in keywords Y or X. John Mueller from Google reiterated this statement on Twitter by mentioning that you should only focus on the things that you actually want to be considered relevant for. Negative keywords can be used in the Google Ads but not in case of organic search results.
Forum discussion at Twitter.