I have received many versions of the same question since I've been writing an atheist blog. I have answered it many times, but it has been a while since I last did so. The question looks something like this:
"I get that you're an atheist. What I don't get is why you seem to care so much what others believe. I mean, what's it to you anyway? Why does it matter to you that many people are religious? Wouldn't a 'live and let live' approach make more sense?"
I figured it was time to answer it again, so that's what I'll aim to do here. Please recognize that I can only answer it for myself. I make no claim to represent how any other atheist might answer it.
Fascinated by Belief
I am interested in the subject of belief from the standpoint of psychology. I find belief and why people believe what they believe to be a fascinating area of study. This is one of the reasons I like to write about it. This interest is much broader than religious belief. I am interested in political beliefs. I am also interested in beliefs we'd describe as paranormal but not religious.
Part of this interest derives from larger interests in skepticism and critical thinking. I am intrigued by how good we are at evaluating some of our beliefs and how bad we are at evaluating other beliefs. The topic of motivated reasoning is a good example of this. We sometimes suspend our evaluation and believe what we want to believe.
That said, I don't care much about what individual religious believers believe. If you derive pleasure from attending church, attend church. If it brings you comfort to imagine that the wafer you are eating is someone else's flesh, go for it. If prayer calms you and better equips you to face the day, have at it. None of these beliefs or the behaviors linked with them affect me.
Affected by Belief
Religious beliefs often influence behavior. When that behavior impacts me or those I care about, I have little choice but to care. If a religious believer decides abortion is not right for them, I can respect this. When the believer decides to ban abortion for everyone else, I begin to care. Consider how some religious beliefs degrade the inherent worth of others. If your religious beliefs lead you to dehumanize others, they are dangerous. Everyone should care about beliefs like this.
This is why I've sometimes referred to "conditional militant atheism." I become more "militant" when confronted with bigotry or the threat of oppression. In these instances, I have little choice but to care.
Religious Extremism
There is a type of religious belief we often label "extremism" that makes our world a more dangerous place. Since this isn't good for anybody, I care about this type of belief. Religious or non-religious, I hope that we all do. Does the average religious believer have any responsibility for religious extremism? Atheists are divided on this question. Some believe that ordinary religious believers contribute to the context of extremism. Others view extremism as an anomaly that has little to do with ordinary belief.
I can see merit on both sides of this debate. I'm not sure religious extremism would exist without ordinary religious belief. I have seen examples of non-extremists providing cover to extremists. Some seek to stifle criticism of religious beliefs, aiding extremists. Then again, some average religious believers are effective opponents of extremism. They recognize it as a problem and fight against it. They are often welcome allies.
Live and Let Live?
This is an appealing sentiment when it comes to many types of beliefs. But "live and let live" doesn't work when it is only applied to one group. Christians working to eradicate same-sex marriage, aren't doing the "let live" part. Telling LGBTQ people to "let live" in this context would be absurd.
For "live and let live" to work, it has to be reciprocal. Both groups have to buy in or it falls apart. Religious extremists are a good example of it not being reciprocal. To their credit, they are clear about their goals. They aim to impose their will on others. In this context, "live and let live" would be suicidal.
If we value freedom, we all have an interest in minimizing the harm caused by religious extremism. Aside from extremism, we can ask ourselves how those asking us to "live and let live" treat us. Are they doing the "let live" part or not? If so, we can extend them the same courtesy.
Image by author via NightCafe