I have one of these things and I have to admit I've never paused to work out some specific conditions when I'd automatically reach for the big red handle first and think later. I suppose I should.
Badly losing orientation in IMC, a heart attack, collision or heading towards something even a sparrow wouldn't land on are candidates. My aircraft is a 600kg and I also fly gliders, so tendency would be that if I still have wings and I can see grass, I'll give it a go.
I applaud this guy. At least he made a decision and did it. Too many people get killed by indecision - I know dithering has nearly had me a few times.