While I'm always one to appreciate caution on the road instead of wreckless abandon, in this case, your counsel isn't universal.
I have spent many a year on the road towing a trailer loaded with all sorts of things. Once year I did 18k miles with a race jeep behind my super duty. There are many stretches of road in the west that are unlike anything you'll see east of Texas. And with a properly loaded trailer the handling is just as predicatable as without it. Its just a different dynamic. On many of the dirt roads I used to tow in on, it was not uncommon to have 8 wheels sliding in the dirt sideways... 4 on the trailer and 4 on the truck.
My point is that its unfair to speak in absolutes. Nobody in their right mind is doing 90 on the 405 with a loaded trailer. But there are stretches where going that fast is slow.