You don't have to answer the door for the Feds. Do not voluntarily talk to the Feds. If they have a warrant signed by an actual judge, then they can do precisely what the warrant says.
But DO NOT TALK TO THE FEDS. Do not answer the door. If you're arrested, your only words are "I want a lawyer."
“Would it kill you to smile a little, Barton?”
“My name is Barron.”
“Nobody cares, Eric. I’m going to tell your parents you’re a pain in the ass, and I’m not dragging you around anymore.”