Communism is not and never was an Atheist movement. The purpose of Communism was to found a collective state, atheism was only of secondary importance.Religion was only sporadically and poorly persecuted because pragmatically when you persecute a religion you create martyrs and that incses the problems that the state has in organizing a country.
Atheism is certainly not a threat in any country to the citizens. Islam CAN clearly be a threat, since Mohammad taught that the ideal is for everyone to be a Muslim. I think that in the first years that the Muslims invaded and ruled Egypt, they tried to forceably convert the Copts and all they did was create martyrs and dissent. Asa result, Egypt has been around 10-14% Christian (Coptic) since around the 6th Century. Egyptians claim to be Arabs, and speak a variety of the Arab language, but genetically most Egyptians probably have more ancient Egyptian DNA than Arab DNA. I am not sure that tests are available to determine this, since Egypt has been conquered and ruled by so many non Egyptians, which resulted in scrambling the DNA so much.