Here's the definitive proof that Diamond City is actually the Enclave in disguise:
First off, some context. The Mayor is a synth and Piper is being prevented from speaking the truth. Already this reeks of distrust. The city is also vastly synthophobic, which may tell an even grimmer tale of a time long lost, where even greater xenophobia existed amongst these people. But why jest? Let's look at the facts:
Exhibit A:
John Henry Eden once said, and I quote: "...I am referring, of course, to our great national pastime - baseball. *snip* ...each state had its OWN professional baseball team. *snip* ...What if the Capital Congressmen could live again? What if they could compete with baseball teams from Pennsylvania, or Maryland? Put your faith in John Henry Eden, great America, and baseball will live again! Comfort, recreation, healthy competition - all will live again! This country WILL live again!"
Exhibit B:
What's Liberty Prime's favorite weapon? It's clearly the Mini Nukes. What does he do with them? He pitches them at the Enemy. And Who is the enemy of Liberty Prime? The Enclave. And if the Enklave gets round orbs pitched at the, then that can only imply one thing - that they're ready to hit the nukes with their bats of ash and hickory - which you're so conveniently able to buy in Diamond City!!!
Exhibit C:
Trevor Miles says that a friend of his once told him that we had to "Fight the Good Fight". Is he referring to Three Dog? And why would he abandon his friend to go to Boston. He clearly isn't a friend at all, opting instead to backstab him at the first opportunity he get's to travel away from the Capital Wasteland and the trauma of watching the Enclave go up in smoke!
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Honestly, I don't know where the heck I'm going with this. I think I need to get some sleep. But the point is that The Enclave likes baseball, and stuff... And Baseball is the best sports EVER.
Have a nice day.