This is again, a ridiculous statement. They weren't much crueler than say, the Romans did with defeated soldiers. Your claims is just plain stupid and have no historical basis.
Have you even BEEN to China and just LOOK at the different "Han" Chinese from one region to the next? That along will show just how ignorant you are.
I think we are still waiting on the far older Chinese civilization to catch up with that level of humanity and justice.
But, to go further, there's a period in Roman history called "The Social Wars". For the most part Rome rose to ascendancy on the Italian peninsula by "merging" with defeated states ~ I don't think even the blindest China apologist would argue any such thing happened in China during the Period of Warring States.
As a brief, I pretty much follow the sort of time-line and opinions about events expressed in this website: http://www.san.beck.org/3-13-Summary.html#2 ~ which is a very, very common timeline.
The Qin emperor was definitely into genocide ~ both BEFORE he became the first emperior, and after he formed his empire.
This is the one period in ancient times that has a death toll due to war anywhere near that regularly experienced in the twentieth century.