To be at least somewhat comparable let's assume it's not a suicide, but an accident, as with the motor cycle driver. These actually happen - people get killed at train crossings pretty regularly in some places.
It matters to what degree you're capable of preventing the accident. The whole point of my post was to emphasize that there are shades of gray, and that it's a mistake to harshly condemn those just over some artificial line while letting those nearly as responsible get off without any consequences.
Of course, as shades of gray go, it sounds like this one is about as guilt-free as one can get: there was almost nothing the driver could have done to prevent the accident; no amount of thinking ahead could have let him slow down enough because trains (unlike motorcycles) take forever to slow down. And you didn't specify the details, those matter - people walking out from behind a stopped bus is unfortunately rather common and predictable. But there are others that do bear some responsibility, for example those building level crossings that lack barriers.
Also note that the aim is explicitly not to be fair, it's to set incentives straight. If you're in a situation that forces you to pay for risks you yourself can't avoid, you're going to get annoyed, and try to fix that situation. For example, by getting barriers at train crossings installed, or by pushing for the city to design safer bus stops, or by discouraging mixing motor vehicle and pedestrian traffic.
If you just shrug your shoulders say "c'est la vie", improvement isn't likely. In unreasonable soundbite style: "you don't like risk taking - reduce the risks, don't whine about how life isn't fair".