As others mentioned, it does look kinda ridiculous in person. Driving home Sunday with my sister we saw one, pointed and both laughed/chuckled to each other. I wasn't looking at the driver so dunno if they noticed, but if they were looking at our faces as we passed they might have been able to notice, and it was just a natural reaction, not meant to have the owner notice in an effort to mock or anything.
Actually, it makes perfect sense. Being a Kennedy is traumatic. Behind the Bastards did a set of episodes on him, and between the deaths and other weird things (including giving them too much power and bad parenting in general) I'm not surprised at all how he turned out.