Is the listing agent a Realtor(r)?
Does listing agent have a pre-established agreement with the seller to kick low-ballers to the curb and stop wasting everyone's time?
Seller and agents need protection against paper hangers. Auto curb kickers are one of those. I prefer the agreement to respond to offers 7 days after receipt. The message you should take to your buyer is 'This one's not THAT desperate!" Isn't that what you are trolling for, desperation?
Is it ethical to allow your buyer to present an offer that hasn't a snowballs chance in Florida of success? At what point are you, the buyer's agent, required to say to your buyer, "This isn't going to work?" instead of deferring that education, time, effort and resources to the seller and their agent.
I would suspect that should you file a complaint the listing agent would be able to produce the aforementioned curb-kicker agreement. Make an fair offer. It's surprising how well that works.