CBS said it had thoroughly checked the background of “Big Brother 2” contestant Justin Sebik, 26, a bartender from Bayonne, N.J. Sebik was removed from the show last week for making physically threatening remarks and then taking a knife to the throat of a female contestant, all the while kissing and hugging her. The woman was not harmed. But, reports The New York Times, a simple check into Sebik’s past at the Bayonne Municipal Court revealed that a Justin Sebik with the same Social Security number as the player on the CBS reality show had been arrested five times in the city — twice for minor robberies and three times for simple assault. The charges were dismissed in all cases. CBS and Arnold Shapiro, executive producer of “Big Brother,” told The Times that Sebik had previously been warned about hostile actions and statements he had made. And a senior CBS executive said that Sebik’s background had been thoroughly checked by an experienced, “highly professional” security agency. CBS declined to name the firm.