Just because the numbers are less doesn't mean that they aren't similar. Obviously, if a genocide was started against both the people of the United States and the people of China, the Chinese genocide would be far worse because they have 3 times as many citizens as the U.S. does. That doesn't make this hypothetical American genocide any less horrible.
And why the trouble recognizing something that happen such a long time ago. Well, while on the subject of the Holocaust, here is a quote that pretty adequately explains why recognizing it is so important.
While persuading his associates that a Jewish holocaust would be tolerated by the west, Adolf Hitler stated...
"Who, after all, speaks today of the annihilation of the Armenians?"
Our strength lies in our intensive attacks and our barbarity...After all, who today remembers the genocide of the Armenians?