Atheists try to hide religion from their children, showing that they hate religion.
Because most atheists are not religious, it is understandable that most atheists aren't going to make an effort to raise their children in an explicitly and deliberately religious environment. Atheists are not likely to raise their children to be Christians or Muslims. Does this, then, mean that atheists are also trying to keep religion away from their children? Are they afraid of their kids possibly becoming religious? What are the consequence of hiding religion from someone?
The idea that atheists might hide religion from their children isn't entirely a myth in some cases, it's true. There are atheist parents and couples out there who are so disgusted with religion that they do everything in their power to ensure that their children are in no way, shape, or form exposed to religion. It's unlikely that they are entirely successful, considering how pervasive religion is in society, but they do try.
Why do they do this? The reasons will vary from parent to parent, but there's no question that there is quite a lot about religion to get upset about. Some may have had very bad experiences with extremist religions when they were younger. Some may have even been abused in a religious context. Others may simply regard religion's emphasis on devotion and faith to the exclusion of critical thinking to be something like a form of child abuse itself.
Some may also be reacting to how many other children are indoctrinated into religion, regarding it as tantamount to a form of child abuse. That's a fairly extreme accusation, but is there any other parallel even remotely like how children have religion imposed on them from the earliest ages? Are any children taken to Tuesday evening classes to teach them conservative political doctrine? Are any children "confirmed" into Marxist economics? Many people would regard such behavior with suspicion at best, and might be receptive to the claim that it's not too far from a form of psychological or intellectual abuse. Parents go much further with religion, though, and react with horror at any suggestion that there might be something wrong with this.
As understandable as such reasons may be, in the end any efforts to completely shield children from any sort of religious exposure or influence are probably futile and may in fact be harmful. Their futility can be understood from the simple fact that, at some point, all children will end up being exposed to religion and theism. It's not possible to keep them from it forever, and trying to do so will end up requiring a great deal of wasted effort.
Of course, that doesn't mean that no efforts to control a child's access to religion should be taken just the contrary, in fact. This is why it isn't the norm for atheist parents to try to completely isolate their children from religion. Instead, most do the smart thing and work to manage their children's exposure to religion. If that exposure to religion is inevitable, then it should be done under supervision and control of the parents.
The most extreme form of control is of course to keep the child away from some particular religious environment and that would be entirely reasonable in the case of the worship services of a church that preaches hatred. In other cases, this supervision might entail personally teaching a child about people's various religious beliefs, attending religious worship services along with the children, and so on. Such actions allow the parent to ensure that children learn the right things and, more importantly, learn to question the religious claims they are exposed to.
All of this is not only reasonable, but it is in fact much more reasonable than trying to isolate a child. Such isolation might itself be considered a form of child abuse because it prevents the child from gradually learning about the way the world really operates. If a child not only fails to learn about religion but also how to think critically and skeptically about religious claims, then how will they be able to deal with aggressive proselytization when they get older? Unfamiliar with the topic and issues, they will be much more likely to fall into even an extreme religious group and all because their parents thought it better to "protect" them from religion when they were younger.
Providing their children with a broad but supervised exposure to religion actually suggests that the opposite of the above myth is true; not only do atheist parents not normally try to hide religion from their children, but they go further than many religious theists. How many Christian parents take their children to religious serves at a Hindu Ashram or Jewish synagogue to teach them about the religious beliefs and practices of other cultures? How many Muslim parents take their children to a Baptist church or Buddhist temple for the same reasons? Most children in religious homes are exposed to just one religion, and from an entirely uncritical, unskeptical perspective. Children in irreligious, atheist homes may be exposed to the beliefs and practices of many religions and from a critical perspective. This should make them much better off in the long run.