I, also feel your pain.
Years ago, my eldest son started his first year in "rookie league". Same scenerio - coach calls with the "congratulatory call", "you've been drafted to play for the yankees".... NOOOOOOOOOOOOOO!!!
then the topper... he asked if I would be an assistant coach, meaning I'd have to wear the uni and hat too.
Now please understand, I grew up 2 miles from Fenway in Brighton, MA. spent many, many summer days and nights at the greatest ballpark in the world. My email address is redsox1974, my license plates on my car are 2REDSOX, we have a mini "green monster" in our yard for whiffle ball, My kids' bedrooms are wall to wall Sox baseball themed, etc.
But the good news is we got through that year, my son has played for the allstar teams every year after, and thankfully has been on national league teams.
The funniest thig though was... when we first got the yankee$ gear, my son, 6 years old at the time, puts on the yankee$ hat with a look of disgust and says... "Dad, I can feel the yankee$ hat burning my head", proving beyond doubt that yes, they are the evil empire.