In the above image, you see a range of different animal emojis. Some of the animals are big, like the whale or the rhino. Some are small, like the snail or the chipmunk. Some, like the eagle, can fly. Others, like the shark, can only swim. Some are herbivores, like the tortoise. The tiger, by contrast, is a carnivore. Fluffy to bald, warm or cold blooded, two legs or 8, there are so many differences between each and every animal in today's image, the only way to encompass them all with the word "animal" is to use the actual definition of the word "animal". Anything else you say will inevitably fall short. "Sorry son, you can't have a hamster, because animals have a venomous sting". See the logic?
Just like animal, religion is a broad term, encompassing a wide range of distinct philosophies. The only way to use the word to adequately encompass all religions is to actually define the word itself. That is, you can say "religions are beliefs about the cause, nature or purpose of the universe". But you can't even say "religion teaches obedience to God", because not all religions have gods to obey (e.g. Buddhism). Neither can you say religion teaches there is only one God, because some religions have multiple gods (e.g. Hinduism). "Religion says", "religion teaches", "religion does" or "religion is" are all statements which, unless used to rephrase the definition of religion, will inevitably fall short.
Why is it, then, that atheists use "religion" and "Christianity" interchangeably? "Imagine no religion", says one meme displaying the World Trade Centre. Would it be nice if 9/11 never happened? Sure. But 9/11 was motivated by only one religion. How would getting rid of any religion except Islam have prevented it? Why should Christianity have to take responsibility for anything done in the name of any other religion on the planet? Trying to blame Christianity for Islam is like trying to blame hamsters for scorpions.
Of course, ultimately, this is a huge compliment. If Christianity is so powerful that unbelievers have to lump it in with everything else in order to defeat it, we must have a very strong case. And we do. Once you set Christianity apart from the other religions, as is proper to do, we have a religion backed by large amounts of evidence. As this post is only really intended to point out the flaw in the phrase "religion says...", I'll refrain from either hurling elephants, or extending the post with examples (but please do search the site for evidence for Theism, as well as for Christianity). All I will say for now is that, once divided from other religions, atheist attempts to criticise Christianity often disappear.
Removing Christianity also allows us to break the rule, as it enables us to say "religion sets itself against God". Sadly, mankind is a sinful species, which causes us to create a wide range of religions. We rebel against our Creator, and as such, we deserve death. But praise be to God, we don't have to take it, because Jesus took it on our behalf. Those who abandon worldly religion, repent of their sin and follow Christ will be spared their due punishment, instead receiving an eternal inheritance in God's Kingdom. If you want to imagine no religion, think of Heaven, where it will have perished forever.