Mmmmm
"wonder how many people would complain if /we/ went to africa, scooped up a few thousand people and made them work for essentially nothing."
Isn't that how the US cotton industry started? Of course the US railways were built with Chinese "slave" labour.
Whatever China's problems, the population get paid for working. Salaries may be low by western standards, but so are living costs.
By the way, Britain holds the world record for fastest steam train. That is about as relevant as fastest diesel in the modern world.
We also have been running 125-150 mph diesels on the main lines since the 80's but now the faster trains are electric. e.g. 140mph commuter trains and 186mph (300kph) Eurostar.
Like China, and unlike the US, we are a crowded land, but with short distances between cities so trains make far more sense than planes - shame we don't get the same level of investment.