Dear James,

It is customary for dignity to act according to local customs as a sign of respect, and I'm sure that Pope Francis was briefed that this is the norm for the region.  Had the statue been of a deity, then it would not be permissible lest it be taken as a sign of idolatry.

Given Genghis Kahn's notorious legacy, it certainly raises eyebrows, but I don't think Francis meant anything other than to honor the local people and the long history they hold.

In general, idolatry can be differentiated from respect when the statues represent deities versus ordinary people. No one would blink if a foreign diplomat entered the capital and bowed in front of a statue of George Washington; they would recognize it for what it was, but when the figure is someone like Hitler or Stalin, the matter is hard to justify.
Peace,