I suspect that wherever there is a rigid dogma, there is someone dissenting from it - either quietly or loudly. In our own day, the hideous spectre of Christian Fundamentalism (and other fundamentalist groups) has given rise to a particularly intolerant form of atheism that cannot see any value in religion at all. Its model of religion is simply "belief in a supernatural deity" and that deity is a personal God, usually accompanied by a literal reading of the Bible (though obviously this is because that is what Christian Fundamentalists believe in). Other, more liberal, forms of religion are dismissed as "not religion" because they do not fit this narrow model. This is rather like the approach of the 19th century Christian missionaries who went to China and assumed that Buddhism, Confucianism and Taoism were not religions because they did not resemble the European religion of Christianity.
Distinguished scholars of religion such as Jonathan Z Smith have pointed out that religion does not exist as such - it is a human-invented category, not a thing. This seems to me to be a much more fruitful approach through which to critique religion. Religions are discourses or languages which describe a particular way of engaging with the world. They involve shared symbolism and culture, and a body of shared spiritual practice. The more conservative forms of religion assume that there are divine laws which humans must adhere to, which curiously enough often resemble their own opinions. This is not a necessary or sufficient feature of religion.
If you assume that all religion involves an unthinking acceptance of a rigid set of beliefs and strict adherence to an outdated moral code, then it's pretty obvious that it should be abolished. No-one could argue with that. However, not all religion does involve these things. If, on the other hand, you observe (from studying it) that religion is a cultural form which evolves over time, then it can be changed and modified and improved (which is what has happened over time). In practice, you can make religious belief a private matter, and not allow religions to dictate what happens in the public sphere (though surely they can contribute to discussion about it, as that is part of the democratic process). But you will never succeed in extirpating the spiritual impulse; and attempting to crush religion and spirituality would be just as illiberal as attempting to crush atheism. So you might as well work with and encourage the liberal, heretical, mystical and dissenting aspects of religion - the thinkers and the lovers.
People brought up in the Christianised West assume that belief (and adherence to a set creed) is a necessary and sufficient feature of religion. That is not the case either; this view is peculiar to Christianity, and to the atheists who have reacted to it. In Islam it is adherence to the sunna which is more important in the case of Sunni Muslims, and adherence to the law which is more important to Shi'ites, according to Albert Hourani's History of the Arab Peoples. In liberal Judaism, the culture is more important; and in conservative Judaism, adherence to the practices laid down in Torah is more important.
The reason that belief and dogma became so important in Christianity is probably because early Christians were being persecuted in this world, they looked to the afterlife to provide them with hope. The idea that Jesus had already been resurrected gave them belief in life after death. In order to shore up this rather improbable belief, they had to create a whole raft of other dogma with which to support it.
A history of dissent
Having created a body of improbable dogma (a Triune God, a resurrected Saviour who was both human and divine, Original Sin, and so on) there were bound to be people who disagreed with all or parts of it. The earliest form of heresy was the Gnostics. (The word heresy comes from haeresis, a school of thought. In classical paganism, it had been perfectly acceptable to have different schools of thought, as it is in Hinduism, Buddhism, Judaism etc.) There was also the Arian heresy (the belief that Jesus did not exist from the beginning of time and so was not an equal member of the Trinity). This was denounced at the Council of Nicaea, but flourished in Europe until the 9th century, and then resurfaced in the Reformation as Socinianism, which ultimately led to the development of Unitarianism. Then there were the Cathars, who were a form of Gnosticism, though not descended directly from it. Then there were the Lollards, who were the first to translate the Bible into English (Wyclif's 14th century translation). After the Reformation, the Dissenters arose. The history of dissent is long and complex, but usually involved disagreement with the unpleasant doctrines of Calvinism, and a move towards more freedom of belief, including the freedom not to believe in things.
Mostly, when a group of nonconformists disagreed amongst themselves, there was then another schism and the group split into two groups with different doctrines. But in the 16th century, a very important development occurred. Unitarians realised that they were never going to agree on everything, and therefore decided to agree to differ, and embrace diversity of belief. As Francis David said, "We need not think alike to love alike". Thereafter, Unitarianism moved steadily towards increasing diversity, placing more importance on the values of freedom, reason and tolerance than on belief. The process was patchy and went in fits and starts (and was accompanied by much persecution from more orthodox groups), but it did help to create more freedom.
Similar developments occurred in Islam with the growth of Sufism. Many Sufis were non-theists, and focused on the mystical aspects of the spiritual path. They emphasised the importance of love.
Some very important groups among the Dissenters were Quakers (the Religious Society of Friends), Unitarians, Methodists, and liberal Baptists (Universalists in America). These groups campaigned for the abolition of slavery, the emancipation of women, education, freedom of thought and conscience, better treatment of animals, and social reform generally. Unitarians were campaigning for the emancipation of women as early as the 1840s. Unitarian belief (as opposed to Trinitarian) had only been legalised in 1813 - previously Unitarians had been persecuted. The list of distinguished Dissenters is long and varied, and includes many scientists (e.g. Isaac Newton, Joseph Priestley), social reformers (e.g. Elizabeth Fry, John Wesley), animal welfare campaigners (e.g. Frances Power Cobbe) poets (John Milton, William Blake) and other luminaries. We are the heirs to their struggle for freedom. Let's not forget their struggle and insult them by dismissing all religion as irrational and repressive. These were people with a profound faith, who worked tirelessly for a better world, and the world is better for their efforts.
Mystical and liberal religion is a very different phenomenon from conservative and fundamentalist religion. Mystical and liberal religion acknowledges and celebrates the existence of other metaphors for the way the world works, and recognises that it's all about feeling connected to the universe and becoming a more loving person.