“…the Federal Reserve has begun winding down its balance sheet. All of these factors increase the supply of Treasury bonds that the private markets must hold.”

I get that the Fed is unwinding QE, but I don’t understand why the private sector would be compelled to purchase those bonds simply because the Fed is selling them. At least that’s what I get from the way the sentence is worded. How do you force someone to buy something from you? I must be missing something.