There are 2 ways of buying ads on Youtube, one is via Adwords and the other is via Doubleclick Bid Manager (a layout on top of Adwords). This year, many ads were shown on unappropriated content for the majority of the Advertisers; after complaining and some boycott, Google introduced Brand Safety measures on Youtube and on Adwords.
In June, Google introduced the Standard Content Filter by default on all campaigns. This filter will exclude tragedy and conflict, sensitive social issues, sexually suggestive content, sensational and shocking and profanity and rough language.
Here the explanation for each filter:
Tragedy and conflict
Excludes graphic footage of combat or war
Sensitive social issues
Excludes videos intended to elicit a response about controversial issues
Sexually suggestive content
Excludes videos about sex or sexual products
Sensational and shocking
Excludes videos of disasters or accidents that show casualties or death
Profanity and rough language
Excludes videos with frequent use of profanity
Content exclusions can limit the reach of the campaigns, therefore using too many category exclusions can increase the price of cost per view.