It's an accusation I see a lot. The inference is supposed to be something like "So you don't believe in God? Fine, but in that case why all the fuss and bother about something you don't believe in? Just shut up, already."
Problem is, those nonexistent gods might not affect us, but belief in those gods does.
Christians in particular, and the religious in general, have what amounts to a state-approved lobby in the shape of the Lords Spiritual—the bishops who sit in the House of Lords.
Equal rights for LGBT people are held back in many countries by campaigns based almost entirely on religious belief.
Abortion rights, the same.
I'm told that climate change is impossible because God wouldn't let it happen. Therefore we need do nothing about it.
Ditto peak oil, or any other possible limit on resources.
Virtually useless abstinence-only sex-education is being pushed into schools, based entirely on religious belief.
Paedophile rapists have been both enabled and protected because of the ludicrous belief that the public image of a church is more important than justice and protection of the innocent.
The mutilation of children's genitals—often performed in unsanitary conditions by people with no qualification in surgery or medicine, and always absent (by definition) of any informed consent on the part of the person being operated on—is excused and encouraged on religious grounds.
Children are regularly segregated into different schools based on the religion of their parents, a policy which creates, and supports the continuance of, inward-looking, self-imposed religious ghettos.
The largest Christian denomination in the world has an official policy that forbids contraception, and enforces this in poorer countries by threatening the withholding of aid. Its representatives have even made the preposterous claim—believed, unfortunately, by millions who don't have the education to know better—that condoms spread AIDS. In fact, they do the precise opposite. This stance and proclamation is tantamount to religiously-promoted murder.
People of no faith, in many countries, or of a faith different to that of the majority, are segregated, discriminated against, imprisoned and even killed, either by their compatriots or their state.
Science education—particularly biology—is being held back in many countries on religious grounds.
Science and research—particularly biology—is being held back in many countries on religious grounds.
The loss of revenue because of tax exemptions to religious bodies and some of their employees, is simply staggering.
Religion may not be—almost certainly isn't—the major cause of war, but it certainly makes a damn good rallying call to persuade young people who might have been doing something good for their fellow human beings, to kill and die.
I have seen children, or semi-adults at most, harassed, threatened and bullied both by other children and by adults, for speaking against religion. Not in some Islamic theocracy, but in the UK and the USA—supposedly free civilised countries.
Children die—again in supposedly civilised western countries—of what should be minor ailments, because their parents cling to the idea of faith-healing.
I certainly respect your right to your private belief. And when that belief truly is private, I'll shut up.