You have far more restraint than I have!
But I'd have tossed the idiot out of there at the first sign of an attitude, and if he scraped up your trailer tearing out of your driveway, then he's liable for that as well. It sounds like a pretty messed up place to deal with. As a business owner, if you have a customer problem with a certain employee, and your trying to make it right, you certainly don't keep involving that same employee with that customer. After the incident, I'd be afraid of what that jerk might do to the boat between the your house and the dealer. He's certainly been reprimanded by the owner, or if not, their all in the same category there, maybe the salesman is a relative or something? I've worked in car and truck dealerships for over 25 years, when a customer complains about a salesman or tech, they rarely give that vehicle back to the same guy. There's just too much of a chance for the employee to try to get even for the complaint, or worse, the boss that reprimanded him. I've been the clean up guy in those situations all too often, having to be the one to deal with the wronged customer who is one step from a law suit and just looking for someone to nail with some wrong doing.
I also know what some sales people can be like, once they get their commission, their done with you. Most likely any repairs or adjustments to be made are coming out of his commission. As will any damage repairs.
I was out looking at new boats today, mind you I own 6 right now, I went to a rather new dealer nearby, a barely 20 something salesman comes out, asks me if I'm looking for a boat, and I bit my tongue and just asked if they sold any bare hulls, as I have a new motor.
The kid came right back and started a sales pitch on a $32K aluminum boat with a brand new motor and aluminum trailer. I stopped him mid pitch and repeated that I only want a bare hull, a wide flat bottom boat with a modified V bow. He then went right into how not buying a motor with the boat and having it installed there voids any and all warranty and how there was a mandatory $360 trailer fitting fee if the trailer didn't come from that dealer. My reply to that was fine, I'll take it home on a flat bed, no adjustments needed.
(Keep in mind that I know the owner of the this place, who was inside at the time, so just let this idiot go on and on). After the flat bed comment the kid goes inside, where I overhear him telling the manager there's some ******* out there who don't want a motor or trailer and don't want to pay any of the costs. He called me every name under the sun not realizing I had walked in the side door and was standing on the other side of the showroom. I slipped into the owners office, who also heard the comment made where all could hear. I let him go on and finish, while the manager kept it going coaching the sales kid how to push a boat sale, and if not, just get rid of me because "Customers like that are more trouble than their worth".
The look on that kids face when he and the manager was paged to the owners office and found me and the owner having a beer and joking about something was absolutely priceless. He, the owner, then did one better buy introducing me as their new manager, (Joking of course). I don't think I've ever seen two guys backpedal so hard as they did. I have half a mind to show up there 8 AM tomorrow just to see the look on their faces again. I'd be surprised if either are there a week from now.
I'd bet money on it you've got the same type of idiots your dealing with, only I'm not so sure the dealer sees what he has working for him. Chances are the salesman is making them money and if so, he's going to be there till he no longer brings in the bucks. Most salesman work on commission only, so if he's dealing with your boat and a prior sale, that takes away from his chances of making money right now. It's a bad situation for all involved.
I would be more upset about the guy's attitude at this point than with then not properly hitching up the boat in the first place. While they are certainly liable, it still was just as much your responsibility to make sure your rig was safe before leaving on the road. Blame who you will, the bottom line was you were driving. But that aside, it sounds to me like the dealer is passing the buck to the salesman hoping he's man enough to make it right, but by the sound of his attitude, that's not going to happen. In which case the dealer will toss the salesman under the bus and finally fix the situation when there's no other way out and he realizes that your not just going to go away.
It's my experience that most salesman work on about a 60% promise fulfillment rate, meaning that they do roughly 60% of what they say they will, and that percentage drops once they have your money. I'm not downing all salesman, but most I've met fall into this category.