bumper sticker

It gets lonely out there when you're braving the highway of unpredictable chaos (terrible drivers, icy roads, snowstorms, etc), and a little humor goes a long way. Probably puts some fuel in their motivational tank. These truckers didn't hold back when they decorated their vehicles with raunchy requests, and vulgar descriptions. 

What is the driver trying to get across here? Are they shaming people for tuna gluttony or vice versa? We're so confused!