I hope they don't trade him, but if you want to get as high of a price as possible for him, then this is a tactic to take.
There are a handful of guys in the NBA that are 'untradeable' other than Lebron, Durant or Anthony Davis- maybe James Harden.
Rondo certainly isn't one of them.
Danny's just trying to send the message that if you're going to call us about Rondo, we aren't picking up unless it's a very good offer at the least.