There's an implication here with a racist connotation - that black people eat watermelons. The 'n------' is short for 'nigger', which is a racial slur that is generally perceived as extremely offensive in a lot of countries.

"They had a watermelon back there for a week and basically called me a n----" There's a stereotype that people with a black skin color really like watermelons. In this case, they placed watermelons in the newsroom where the news anchors could see this. This is something one of the black news anchors said. He means he feels racially insulted, because he's black and they're trying to provoke him. "They're basically calling me a n---". They didn't call him a n---- but it feels as such.

Sorry - I have no idea!