Yes they are just words and not just negative ones.    They are both used in many fashions and manners and are not solely associated with the British empire or atrocities.  
You should go to the South.  spend some time in Louisiana.   While there are racial tensions there, they don't slap everything as a negative.   It is part of the past, it is history.  She's not serving "Slavery Slapjacks."
Just look up the word plantation.  It's a farm.  That is the definition. 
I feel the reaction is misplaced and the name is read too far into.   If you protest this place why aren't you protesting every Cajun and Creole food spot?    Are you protesting any Indian food place that serves food on a table with porcelain plates?  As prior to the British influences they typically ate on the kitchen floor on banana leaves (look it up).   Or Taiwanese using Japanese rice wine in their cooking...(50 years occupiers).  Seem extreme?  Yes, so does reading more into this name other than it is fusion food.