art is often controversial because

 Well, art is often controversial, because it is sometimes based on the religious beliefs or also the cultural circumstances of certain people... ~Meaning, someone may draw something about jesus, and people may consider that controversial... Because they may not believe in that god, or other reasons that involve the religious beliefs of people. ~Hope this helped! :)

Art is often controversial because of the subject matter. Artists often choose subjects that are taboo in ordinary social situations. This could be as simple as depicting a nude image of a human being or as complicated as addressing a moral issue like abortion or a political issue like war