I'm an RV salesperson. I do not sell trailers that are too heavy for my customers' vehicles. Now let me tell you of those customers that insist on towing a 43' destination trailer across country with a 1/2 ton. In one case, he had his friend tow it off our lot, then he hooked his 1/2 ton off and went south.
Yes, salespeople shouldn't sell something too heavy. But we as consumers ALL owe it to ourselves to know what we're driving and what we can tow. Every day I have people who walk in here with a 3.7 Ram pickup that they are convinced can tow 10K... It works both way folks!