I read once that many modern atheists equate all of religion with Eastern religions (That is, ones such as Buddhism, Zen, Confucianism, etc.). That is to say, they believe that all religions should be handled the way that Eastern religions are.
Western religions (Christianity, Judaism, Islam, in particular) are, by their very nature, exoteric. This means that they are meant for external, public display. This doesn't mean you go out into the middle of the street and proclaim your faith in Christ. This means that you worship as a group, with other people, and as part of a community. Western religion has also been accessible to large groups of people, meaning that it is made for large groups of people (the scripture is accessible in colloquial language, the spirituality is very visual and tangible, and the worship is public).
This is in contrast with Eastern religions (I don't have complete knowledge of eastern religions, but I'll try my best), which, by their very nature, are very exoteric. They are made, and meant to be, one of private, solemn, and internal reflection. Traditionally, this means private meditation in the privacy of one's home. Yes, there are group gatherings, but they are not the center of the religion (in contrast to especially Christianity, where the Mass is our greatest prayer). In eastern religions, one meditates and reflects on the precepts of the religion in the privacy of one's own home, dwelling, etc.
The failing comes when you try to equate one with the other, which may be a reason that many atheists say what you posted about. They identify more with eastern religions (lack of strict dogma, variety of different paths, the lack of deities), and so they come to believe that all religions should be like that. This is simply false. You cannot ask a Christian or a Muslim or a Jew to exchange their group prayer and worship into private reflection and meditation. By the same token, you can't ask a Buddhist or a Confucian to do the opposite: turn their private reflection into communal praise and worship. To do so is to ask them to betray their religion.
In addition to the above, many atheists also believe that you shouldn't have religion in politics, etc. When they do this, they equate a particular moral teaching or moral point with religion. This does not follow. A specific moral teaching does not have to be equated with a particular religion, especially if said moral point can be proved or made through reason without reference to religion (this can be done for many things: Abortion, birth control as harmful, no-fault divorce as being harmful, etc.). So, just because a candidate is pro-life, doesn't mean that they are trying to force their religion on others. Morality does not wholly make up religion, so to say that a particular politician has a certain moral view does not mean that they are trying to force the religion (or irreligion) on another, just that they hold a certain moral view.