Having lived in Red Sox Nation* for the greater portion of my life and never having an interest in professional baseball, I have to say, I'm not quite sure of the way this manifestation of fandom works.
Now I don't live in dark cave nor am I visually impaired; I've seen the anti-Yankees stuff. The Yankees Suck t-shirts. The Calvin peeing on a Yankees cap car decal. I'm aware of the rivalry. I'm also aware of the generally high level of fanaticism among Boston/New England fans.
But I was pretty shocked to see a guy wearing a t-shirt that said "A-Rod slaps balls". I wonder how he explained that to his young son who was shopping with him. "You see, son, slaps balls is a double entendre meant to convey the Alex Rodriguez likes playing with men's genitals which means he is gay, which makes him less of a man and thus less of a ball player even though he just set that record. Because all the people we don't like are gay. Even if they aren't, we call them gay. Because no one likes gay people. Get it?"
Given the largely unchecked name-calling and bullying based on anti-gay sentiments that happens in schools these days it's possible the son doesn't need any explanation.
Then when I was googling to see if I could find the t-shirt, I found other anti-Yankees slogans like this one: "Derek Jeter drinks wine coolers". I'm going to skip the sarcastic, fictionalized conversation for this one. I think we all get it.
The fan board I was on (it was a Yankees site) had one fan reporting that he had seen a t-shirt that said "Derek Jeter has AIDS". If that shirt really exists...well I don't think I even have the words if it does. The first one is bad enough. The second one is beyond the most basic level of decency.
Here's a slogan for you:
Homophobia and misogyny: As American as baseball and apple pie.
*TANGENT: Isn't it interesting how we recognize the nationhood of a group of sports fans but fail to recognize the nationhood of people like, say, American Indians. I realize that we aren't talking about laws and sovereignty here but the fandom~nationalism connection and how language is used to construct fandom is interesting.