Fact of the matter is they can practice religion. Not to the extent they would like to but that is a far cry from forced atheism. Until China actively eleminates religion across the board, not just saying 'you have to worship in our church', then they arnt trying to force atheism on anyone. That doesnt make what they are doing right but then that doesnt make the idiotcy of claming that Communism is an atheistic entity hold any more water.
Actually, suppression is the wrong word to use in this instance. Suppression means to put a stop to something, to abolish it, to eleminate it, which isnt what is happening. It could be arguing semantics but I have yet to see anything from communist states that shows they are actively trying to eleminate religion as a whole as opposed to limiting their ability to challange the state as the 'ultimate' authority to the people.
Limiting it is a better word since even at the height of Stalin and Lenin, 1/3 of the USSR population openly admitted and practiced their religion(hell, the USSR even tried to establish a 'Zion' for Jews, which isnt an act of an atheistic state).
There is a big difference between a state saying 'Well, we will allow you to practice religion, but only if you do so in this way' and a state saying 'There is no god, if you worship a god you are breaking the law of the state'. Ultimately, the practice of limiting religion under communist states isnt done with any ideal of Atheism in mind. It's all about controling where the power is.