I don't quite understand why the LT needs such a high load rated tire. My Harley FLH weighed in at the same if not more than the lt, and it didn't need any special tire, yet the Lt needs this incredibly high rated very hard to get special tire. Are people over reacting?
I am not a tire engineer, but I am an engineer and have read a little about motorcycle design (started with Gordon Jennings and included folks such as Tony Foale). Let me offer you a few things to consider.
Motorcycle components are designed for the bike's GVWR, not the empty weight. I am not sure the specs for the FLH, but few bikes match the LT's gross weight rating.
Speed is another factor. High speeds generate heat and the tire needs to be able to handle that. Speed ratings generally are more of a heat rating than a strength rating, although both matter at sustained high speeds.
Lastly, dynamics matter. Every structure distorts under stress and vibrates at a specific frequency based on mass and stiffness. I can pretty much guarantee that the LT's chassis and suspension are much stiffer than the Harley. This likely puts more stress on the tire as well and may well require a stiffer sidewall. Higher load rating likely gives more stiffness and the LT requires even more stiffness yet, hence the special REINF requirement.
Since there is no tire spec for stiffness, the engineers may well have used load range as a surrogate to get stiffer sidewalls, even though the GVWR alone may not have required the 79 rating. Engineers in all fields do this all the time.
Components like tires are complex systems needing to meet many requirements simultaneously and the specified attributes are interrelated in complex ways and can't be looked at independently. Novices think that only load affects load range and only speed affects speed rating, but a given tire is specified because it works as part of the total system. This includes things like dynamics that can't be specified directly.
Using a tire other than that specified by the bike maker means you are now a factory test rider which is fine as long as you accept that responsibility willingly and inform your passengers. You may never have a problem, then again, you may hit just the right bump at just the right speed to excite a resonant mode of the tire and suspension that triggers a fun tank slapper. "Are you feeling lucky?" to steal a Dirty Harry phrase..