"pot calling the kettle black" is a traditional saying used to describe someone who accuses another of doing something that they themselves are guilty of.
Example of use.
Jimmy's pants are too tight. He goes to school and confronts Billy for wearing pants that are too tight. An onlooker might say... "Look at the pot(Jimmy) calling the kettle(Billy) black" .... you know, because both a pot and kettle are made of iron and black, or at least they were at the time of this saying's origination.
That is your urban dictionary lesson for the day.
I would also like to add that this is the offtopic section, while it is not directly suggested that politics be discussed here, some things of a political nature may fall under the description of "100% useless BS".
Example, if i were to seek a conversation about Obama's economic policy. Politics forum.
If i wanted to comment on Obama's history as a closet homosexual and post photoshop images of him going down on a biker dude at mardi gras. Off Topic.
That concludes our lesson for the day.