You are really anti-Christian because you spend all of your time on Christianity.
Although this is by no means true of all atheists or atheism itself, there is some validity behind this perception and it should be taken seriously. There is no ignoring the fact that many atheist web sites and atheist books spend a great deal of time with the doctrines and beliefs which are specific to Christianity or, at the very least, to traditional forms of Western monotheism while at the same time ignoring other religions and more general theistic beliefs. Why is that?
First, this occurs because most of the atheists involved live in Western countries where Christianity and monotheism have dominated culture, politics, and society for over 1,500 years. This means that the atheists are most familiar with Christianity, have to contend with Christianity on a daily basis in their lives, and perhaps even were raised as Christians. In some cases, people may even be atheists (or at least started down the road to atheism) because of dissent from and/or resistance to Christianity's cultural hegemony. All of these are valid and understandable reasons why Christianity is more of a focus for atheist critiques than other religions.
If Jews came to online communities to convert atheists or if Hindus came knocking on our doors to share the Hindu faith with us, atheists would likely critique them as much as they do Christianity. If Buddhism were as significant of an element of Western culture as Christianity, it would probably be critiqued much more extensively. That isn't the case, though, and the reality we have to deal with is the dominance of Christianity where we live. Thus, it is unavoidable that Christianity will play a major role in atheists' critiques of religion.
Nevertheless, this does not always justify how big of a role Christianity plays in those critiques. Sometimes, books on atheism focus on Christianity to a degree that simply isn't necessary. It might be understandable because most of the book's readers will be familiar with Christianity, but I think that it would make more sense for those authors to widen the readers' horizons by making the critiques as general and broad as possible, at least when appropriate.
In addition, it is true that some atheists are vehemently anti-Christian. It isn't simply that they object to religion and, hence, object to Christianity. On the contrary, they display an almost unreasoning hatred for everything associated with Christianity even to the point where they can act downright irrational about the entire matter. This is unfortunate, but it's also often understandable.
It must be remembered that some atheists come from a Christian background where they were discouraged from doubting and questioning. Once they started, however, the found that they had been deceived and lied to by religious leaders. This can easily result in a lingering resentment and even hatred of the religious beliefs and power structures which allowed such deception to occur and allows it to continue. At the very least, experiences like this can lead to a phase in a person's life when they are angry and resentful towards religion generally and Christianity in particular.
Some continue to suffer from discrimination and abuse from family, friends, or colleagues. They often feel unable to even reveal that they are atheists for fear of reprisals and ostracization. In such situations, it simply isn't possible to expect a person to have warm, fuzzy feelings about a religion which is used, from their perspective, to foster hatred and repression towards them simply because they are unable to adopt that religion. Christians who find such anti-Christian attitudes disturbing should probably focus on eliminating the persecution and hatred those atheists endure in the name of Christianity rather than trying to convert those atheists to Christianity.
Most atheists who have to contend with such experiences manage to overcome their anti-Christian feelings, but not all do. In no way, however, does such hatred have any implications for atheism itself. Even if all atheists happened to hate religion generally or Christianity specifically, that would not mean that atheism itself is unreasonable and theism reasonable. At most, it might simply mean that atheists sometimes adopt unreasonable positions and that's assuming that the atheists' hatred is itself unreasonable, which it wouldn't always be.