Okay, call me crazy (shut up!), but it's not the frickin' watermelon that's offensive in this scenario. I think that the person quoted in the article mis-spoke.
I love watermelon -- eat it several times a week, even in the company of white folks
. Seeing a picture of watermelon or someone with a t-shirt with watermelon on it isn't going to offend me. However, if I see someone with an afro wig and face darkened so that they look "black", then yes, I'm going to feel put out and rightly so.
I now return you to your regularly scheduled lives.