China isn't atheist. They primarily are Buddhists and various forms of Shinto (generally classified as 'folk religions' by the Western world). Shinto, although it is a Japanese word, is actually a religion that exists in many parts of the world, including the United States. Most people call this religion a 'folk religion' sooner or later.
There are Christians in China, but they have to stay hidden to avoid persecution.
Islam believes in God, meaning the same God as the Jews and as many Christians. Like the Jews, they do not recognize Christ as a god or as the Son of God. If anything, Christ was a great teacher, but not the Son of God.
Islam has its fundamentalists like any religion. So do Jews. Unfortunately, cruel dictators wield power in the name of Islam, corrupting what this religion is, and use it to push their wars and hatred of anything not Islam abroad.
Both Protestants and Catholics have caused problems, and both have had their successes. As always, there are those that push their own agendas in the name of some religion, using it to masquerade what they are doing. These are the ones that cause the most problems in any society. The liars. The deceivers. Those that follow the pattern of Satan (using the character as described in the Bible) or the pattern of puffed up pride among men (as described in the Bible).