Now the logic of "only 25% of bad outcome" is the real gambler's fallacy here. How far would you push it ? Would you pull the lever if it was a 20% chance of killing 10 ? A 10% chance of killing 50 ?
This reminded me of one of the ways of explaining the Monty Hall problem (if there were 100 doors and 98 got revealed as empty would your switch). If there were 100 alternate tracks, 99 of them empty, and the other with 200 people tied to it, I would pull the lever.