This explanation, while true, doesn't fully explain why nobody* was using explosive or incendiary weapons in Dune - even if shields protected against overpressure (I recall nothing to support this), they certainly didn't protect from fire, heat or the lack of oxygen. So for me the shield-lasgun reaction was sort of handwave on Herbert's part to curb overpowered lasers and have his swordfights. BUT if lasers were so powerful, why not use the same power source to power a railgun... If it hits the shield, it will be absorbed, but a close-miss would probably generate enough of a blast wave to kill a shielded enemy... In addition, energy cannot, as far as we know, be generated out of nothing, so it seems each shield was carrying a power source worth at least several kilotons... which generates even more questions.
Surely, culture can explain a lot of things - it is true that nobody wanted a real war in the Empire, as it could potentially overthrow its social order (how shaky it's been is clearly shown by the success of Paul's crusade - if the Empire was solid and cohesive, he would have no chance of succeeding with what little forces he [only initially I presume] commanded).
Also if a lasgun provokes such reaction... laser is nothing but EM radiation. Why the shields didn't explode when exposed to sunlight, UV, radiowaves, cosmic radiation, etc...
*with the exception of Harconnen siege of the Atreides' palace on Arrakis, but I bet they did it more to show they're bad boys than out of practical reasons.