I'm actually a little surprised by this, if only because it seems in recent years major league sports have been pretty intimidated by the forces of political correctness. Which is to say: They know who will scream and boycott if they don't give them what they want, and all large, high-profile institutions want to avoid the bad publicity that comes with such things.
Oscar Lopez Rivera is a terrorist responsible for more than 100 bombings, but that's old news. The new news is that Barack Obama commuted his sentence on his way out the door, which makes Rivera a new left-wing icon. He is also a bit of a hero to some people of Puerto Rican heritage who don't really know the full story of what he did. The Fire Department of New York knows it, though, which is why they're skipping this year's annual Puerto Rican Day Parade after the organizers decided to honor Rivera as part of the festivities.