An emergency exists when the pilot declares it; the ATC perspective is
irrelevant from that point.

Not at all true. If ATC's perspective is that a 767 on short final for
runway 35 will not be able Go Around or Clear the Runway with out
creating a collision hazard with the Emergency aircraft landing runway
17, then ATC has every right to deny the pilot runway 17.

If runway 17 was the pilots only option then he need to let ATC know
that.

The Pilot had every right to request it.
ATC had every right to deny it. (in this case it ended here)
The Pilot had every right to insist, at which point the Pilot would
have to explain why (he had turned down two closer runways and must
runway 17)
ATC has every right to insist as well but would have explain why he
could not use Runway 17. (Example, Departing aircraft runway 17)

Brian
CFIIG/ASEL