This topic engenders lots of emotional discussion about once a month on virtually all of the RV forums. IMHO I wouldn't be without a supplemental braking system regardless of state law issues. As one person posted on a thread about this a few months ago, you no doubt have >$100k invested in your MH and probably >$25k in your toad plus all your possessions and, of course, your family. Therefore, why would anyone quibble about a safety investment of <$2k?
As a retired physics teacher, I will agree that >90% of the time all of our coaches will be safe with toads that do not exceed the MH tow rating. However, I can easily describe scenarios in which the safety margin is greatly reduced or vanishes completely. FWIW, I think that's what insurance is for, to protect against what people call "low probability of occurrence, high impact" events.
BTW, we have a ReadyBrake system integrated into a ReadyBrute tow bar. You can also add it to any other towbar. It is relatively inexpensive and simple and has worked well for us for 15,000 miles.