Except India's CO2 emissions are less than a third of China's, despite having more people. End of story really. Per capita is a nonsense argument by someone trying to win on technicalities. Unfortunately, "the earth" doesn't care how many people a particular country has, it makes no difference to the environment.
It might make a difference if they were actually using the C02 to do something worthwhile, instead they're using it to make goods to sell for a profit. It's about profit and has nothing to do with China being an developing/industrial country new to the game.
Per capita is a common sense rather because more people further developed hence more industrialization and more CO2 emission.
Along the same lines, smogs and air pollution are also part of the emission that had happened badly for the major industrial hubs in the western world like London[1] and Los Angeles[2] in the early 20th century. Although most developed countries has realized the environmental impact of industrialization and the cost of repairing it.
It might make a difference if they were actually using the C02 to do something worthwhile, instead they're using it to make goods to sell for a profit. It's about profit and has nothing to do with China being an developing/industrial country new to the game.