My comment is actually fairly objective. I happen to think it might actually be too nice a characterization of people who might be inclined to do such things.

Here's the problem. Let's assume you are right and I am wrong. The person is not an idiot. The person in question is a very intelligent man, highly accomplished in his chosen profession and perhaps even holding an advanced degree from a top university. In other words, someone who would be almost impossible to characterize as an idiot.

OK. Excellent. With that establish, let's examine what this person did: They are doing the equivalent of placing a six to eight pound (or more) incendiary device 200 feet above people or property.

Yes, LiPo's catch fire when seriously damaged, therefore it is perfectly reasonable to characterize them as incendiary devices.

The potential energy of a 6 lbs object at 200 ft is 1,629 Joules.
The potential energy of an 8 lbs object at 200 ft is 2,174 Joules.

OK, what does this mean anyway?

The muzzle energy of a 44 Magnum round is approximately 1,400 Joules.
The muzzle energy of a 50 AE (Desert Eagle) is approximately 2,000 Joules.

Not an apples-to-apples comparison, of course, rather one to develop a sense of proportion. We can probably say that flying a 6 to 8 pound object 200 feet above people or property is roughly equivalent to potentially shooting a 44 Magnum or Desert Eagle at those people. Again, a rough comparison only for the purpose of trying to evaluate how dangerous it might be to engage in such an activity.

And so, this really smart and considerate person goes ahead and flies such a gizmo above people.

What's the thought process and what is the motivation?

You see, if the person is an idiot when it comes to making such decisions the answer is easy: It's just another idiot.

However, if they are not. If this person is doing this with full command of the facts and full understanding of the risks involved then, well, we might justly be able to characterize his actions as being intentionally and negligently criminal or worst.

My point, in many ways, is that calling them "idiots" might actually be kind. In fact, IANAL but I would suspect when the day comes that someone kills a person with a toy drone we are going to see a temporary insanity defense. Being an idiot, in that case, might actually be an asset. Not one of these people is going to go up in front of a judge and claim to have been fully aware of the risks and issues while deciding to purposely fly a device into the position that ultimately caused someone's death.

To change the frame of reference in order to make it even clearer: What do we call someone who goes to a public park full of people and kids and starts shooting a gun up in the air in random directions. Well, at best. At best. An idiot. In reality, they would be arrested and charged criminally. So, again, calling them "idiot" is actually being kind. The scenario is indistinguishable from that of flying a heavy drone on top of people. They can kill, just like a bullet. Unlike a bullet, they can start fires which can, in turn, easily kill tens or hundreds of people.

So, yeah. I don't see any way to agree with your perspective.