I am going to say it straight out, "The salesperson is just trying to make a sale."
We had a GMC truck 5.2 V-8, rated to tow 9,000 lbs and towed a TT with a weight of almost 5,000 lb. Hubby was not a happy camper towing the TT, especially on steeper hills. He traded for a 250 diesel. What a difference that made...the diesel didn't even flinch with 5,000 lbs. behind it.
Anyway, we now tow a 5ver Keystone, similiar to a Cougar. NO WAY will you be able to tow a 5ver any distance...Wait, the dealer sort of is telling the truth....You could tow it to the nearest campground and leave it there.
Better get at least a 2500/250 Chevy, GMC or Ford or a diesel if you are going to do any amount of traveling with the 5ver.