This pretty much nails it, that is why things have to be very different with Thorium and the combination "very different" and "nuclear" leads to an over abundance of caution.
One of the reasons the travelling wave reactor is "interesting" is that starts and ends with 'low grade' radioactive material, and works very much like a 'brushfire' which burns fuel ahead of it and leaves behind fully utilized fuel. The downside is that it doesn't really "stop" in the sense that you start one of these candles burning and for the most part it goes 10 years and then sputters out, you can harvest the energy or not but you can't really turn it off. (at least not in the early designs)
So much of the engineering issues with Thorium are mastering the fuel cycle and that is something the US DoE hasn't spent a whole lot of time investigating. Its an interesting question what we could do with a 1950's attitude toward researching nuclear power uses and 2010's level of technology.
We have different definitions of "difficult" I suspect.
The Thorium fuel cycle produces U232, that stuff kills at a distance, through walls. What that means is that there are a number of scenarios, one of which Fukishima just went through, where the core gets uncovered and rather than leaking Cesium it shoots gamma rays everywhere killing anything trying to get near it. That is not the case with the U238 fuel cycle.
Not saying it can't be dealt with, just saying its different, and by being different it is dangerous in different ways.
"The Thorium fuel produces U232..." Yup, which is one of its nicest features. It means that the U233 is unlikely to be used for weapons. And since it never leaves the well shielded containment area in a LFTR, there is no hazard.
If the kettle is breached in the LFTR, the salt will probably just condense on any small break and seal it. If the break is large, the salt drains into a drain tank which is still in the shielded containment volume. No worries, mate! Oh, and since there is no significant pressure and no volatile chemicals like liquid sodium, there are no forces trying to disperse the materials. Inherently MUCH safer than any PWR or LMFR.
One of the reasons the travelling wave reactor is "interesting" is that starts and ends with 'low grade' radioactive material, and works very much like a 'brushfire' which burns fuel ahead of it and leaves behind fully utilized fuel. The downside is that it doesn't really "stop" in the sense that you start one of these candles burning and for the most part it goes 10 years and then sputters out, you can harvest the energy or not but you can't really turn it off. (at least not in the early designs)
So much of the engineering issues with Thorium are mastering the fuel cycle and that is something the US DoE hasn't spent a whole lot of time investigating. Its an interesting question what we could do with a 1950's attitude toward researching nuclear power uses and 2010's level of technology.