Update: As I was writing that post from my phone, I couldn't expound that much. But I thought that I should say that Eli and I have engaged in a number of thought experiments about how to make the above graffiti grammatically correct. In all instances, it presupposes the existence of a person named Tomato. Here's a hypothetical exchange:
Eli: My brothers aren't married, but they're straight.
Fargus: My brothers are straight too, but Tomato's are gay.