Answer: Yes, but sometimes it could get you in trouble.
Explanation: I quote the definition of art "the various branches of creative activity, such as painting, music, literature, and dance." The use of graffiti could affect what society views it as (gang affiliation, unnecessary loss of tax money, etc.) However, graffiti is indeed art, as it is a way to express emotion, even if you don't use that fact in the nicest of ways.