It's not so much the safety police, as the stupidity danger to others police.
It's this sort of ridiculous rationalization that makes people think unsafe acts like this are okay. For one, he was actually closer to 3K pounds over weight on a 7K GVWR trailer. Most 7K trailers weigh about 1,800 pounds. Throw an 8K pound machine on it, and you're overloaded by a full 40%. Does that sound even remotely smart?
Further, the whole "go slow, drive carefully, and it'll be okay" is total hogwash. You can't control what the other idiot does, and if they do something stupid, like pull out in front of you, without looking, and you hit them, you're going to burn when the police figure out you were drastically overloaded...which might result in criminal charges, like the case I linked above.
How can I say that? Years ago I drove cement mixers, dump trucks, transfer trucks, etc...all summer jobs during high school (it was pre-CDL days) and college. One day I was rolling along right at the speed limit (35mph) in an empty mixer truck that weighed somewhere around 25,000lbs with an empty barrel. It was late morning, right before lunch, perfect weather, dry, level road, and nobody in front of me. As I approached a traffic light, there was opposing traffic waiting to turn at the light, and then an elderly man made a right on red through the intersection, pulling out in front of me…he never looked. I jumped on the brakes, hit the air horn, and moved over as close as I could to the opposing traffic…all to no avail. I got it slowed down pretty well before the impact, but the results were still horrible to look at. The car (brand new Cadillac) was nearly folded in half, and ripped open from the driver's side rear view mirror to the tail lights. Luckily both passengers survived...barely, by mere inches. If I had even a partial load in the barrel, they both would have certainly died because I wouldn't have been able to slow nearly as much as I did. Perfect conditions, barely loaded truck, fast reactions (I was 20 or so at the time) and a lot of luck were involved. I STILL got called in to face charges that I ran the light, but luckily I had several witnesses from the opposing lanes that testified I clearly had a green light (which they also had), and that I had done everything possible to avoid the accident. The investigators determined my speed was actually a bit under the speed limit (1-2mph), based upon the skid marks, but the "victims" still filed a complaint. I was lucky to have a family friend who was an attorney represent me, so all it cost me was a bottle of Johnny Walker Black, and the judge threw the case out almost immediately. If I had been doing anything wrong at all, I would have been SOL.
In short, you can try being as careful as possible, but when you start out doing something dumb, other people can get hurt because they don't know you're being an idiot. Seriously, what would a flatbed have cost for this trip, $100? It's called the cost of doing business, and being a responsible citizen.