It all comes down to politics. Were politics not infused with religious ideology, I would not give so much as a single shit what any individual's personal theology was. We could live, and let live. I like blue, you like red, mix nox.
However, when governments create, and are encouraged to create, laws that incorporate the religious views of one group of citizens into the enforced policies that affect the entire population, then it becomes a concern for me, and other atheists. Now, your beliefs affect me. Government creates a problem when it imposes, through enforced laws, your religious positions on me. I'm certain that Christian, Muslim, or other theists would very much understand this position
The United States, in spite of the First Amendment designed to separate Church and state, is a highly religious country, ruled by increasingly aggressive religious political leaders. The globe is littered with examples of failed attempts to incorporate religion with governance. My concern is that one day America might be counted among them.
It is for this reason that, as an atheist, the beliefs, and actions of theists concern me.
Most don't really except when theism is being shoved in their face and they are being told they are sinful, evil, deserving of horrific punishment or just wrong for thinking on their own, with the mind nature gave them.
Seeing people in a hypnotic state of some religion and unable to use their minds might be bothersome.
Faith in the heart of something beyond themselves is good in some cases, it motivates is to aspire to be better. Absolute obedience to some idea of a creator manipulating us because man wrote it down and used these ideas to control other people is not, it's a form of slavery.
I don't know that many atheist that are zealots, but I have seen FAR too many, and results, of religious zealots who can't think and act beyond their own dogma.
Spiritual, internally, I'm a little in awe of. Religious, not at all. Don't care much one way or the other, except historically or politically. Religion served a purpose to the evolution of civilization. Extremists/zealots, sorry, I don't have much patience for and see them as potentially dangerous in their some of their ideology.
I grew up around religions, learned to have respect for many religions, studied religions, exposed by children to religions, understand the place religions can have for some people. I've seen the best and the absolute worse of religion. I cannot believe in a god, at least not in a creator monotheistic type. There might be some as yet unexplainable force or energy out there, but handing out rules, passing judgement and playing with our lives, seeing humans as anything special or in god's image............... not in the least.
it's not logical
Some call it faith, I see it as delusional and in some cases downright deadly, potentially to all life on this planet. Dangers have been proven historically and in present day.
Love? Worship? Obey? Why does such a creator god need our devotion or even recognition? There is a universe(s) and some god is concerned about a few billion humans on this one planet?
Live a good life, if there is "something" be pleasantly surprised. Spend time worrying or praying, or worse fearing? Waste of time and energy, better spent on a search for knowledge and kindness to others.
Personally I don't belong to groups, beyond the family. I'm american by birth and choice, but I was raised globally. No religion since I was 10. No political party. No organizations, except my service to in the military decades ago. I care for life, because I've too much harmful death. I care for the relief of suffering, including the dying, man or animals.
No religion, past or present has moved me enough to believe or fall in line to some myth or dogma, not even those I was raised on.
Hypothetically, if there was something akin to a god, I don't believe it should be feared or use fear to control.
If there is a creator of some kind, love is unconditional, it does not require obedience or worship or praise of any kind. It creates and it lets go.
Rules, laws, religion are the work of man to control......not a god
Awe of the force of nature brings caution, not punishment or judgement for personal actions or thoughts. Nature nor science are emotional or judgemental, nor do they demand or require anything from us. It just is.