The claim is often made that atheism is immoral and that religion is essential for any moral life to be lived yet the evidence suggests nothing could be further from the truth.

• Wasting Time: Religion is a waste of time and effort, and I mean that literally. A tremendous amount of time is wasted on invisible/unprovable things such as gods, devils, heavens and hells etc. This especially appalling because, as Dawkins puts it, the Christian god is, "the most unpleasant character in all fiction: jealous and proud of it; a petty, unjust, unforgiving control-freak; a vindictive, bloodthirsty ethnic cleanser; a misogynistic, homophobic, racist, infanticidal, genocidal, filicidal, pestilential, megalomaniacal, sadomasochistic, capriciously malevolent bully." ("The God Delusion"). There's the amount of time the religious waste celebrating and/or praying to such unprovable (and unpleasant) deities as well as that preparing for a supposed afterlife.
• Societal Restriction: Religion (archaic belief systems in general) place societal restrictions on us, worse in the US than here and seemingly worse still in middle eastern countries. More importantly, and one only has to look at our *beloved* monarchy as an example of this (especially in light of recent news reports), I think there is the way that certain classes in society use religion to hold the masses down, in that sense religion is clearly a tool that is used to keep others in "their place". For the more rational amongst us, this can be especially distressing when we are faced with examples of religious bigotry and especially when the religious claim that their right to be bigoted trumps rights that have been hard fought for and the way they generally seem to oppose progress towards tolerance and equality. That said, being somewhat topical, I begin to wonder if my belief that we were getting more tolerant and more open is something of an illusion since, following the Brexit referendum, there seems to have been an upsurge of right-wing extremism, an ugly undercurrent to our society that we ourselves have fostered by not grating a platform to those voices (we simply didn't know they existed)..
• Religion Is Good: We are, as a society encouraged to show respect for faith with no obvious reason why. By that I refer to the apparent general belief that religion equals good and that a lack of it is bad. It's something I strongly suspect is based on a deliberate campaign, decades, perhaps centuries, old that has tried to make atheists and heretics appear immoral. I think it's one reason why some are reluctant to call themselves atheists and prefer the term agnosticism when the positions are pretty much the same thing. Ask yourself how many times you have heard people on The News reported as "good Christians with blah blah blah" then ask yourself how many times you have heard them say, "a good atheist..." the answer is it never happens.
• Religion Promotes Violence: In the US people have been reported to be beaten and sometimes killed as a direct result of religious beliefs. We Brits often laugh at the Americans but as I once predicated about the rise of creationism a year or so after something hits the US it typically hits us too. Look at Trump and then look at Johnson!
• Misuse Of Resources: Religions can claim charitable status for no obviously justifiable reason and there are reports that UK based religious charities promote harmful views. And, of course, that brings me to one of my favourite subjects the Faith School system for which I see no justification at all ... even those who are not religious seem to have fallen for the myth that religious schools provide better education when, if there is any truth in it at all, it is almost certainly a result of catchment (better students attracted) rather than inherent quality.
• Ignorance: Religion engenders ignorance. It encourages people to be satisfied with answers that are given rather that sought (science), it teaches people to stop questioning. How many times have you heard people say "Oh, I'm not a scientist" as if it's some kind of virtue? I am not "a scientist" either but I am a science adherent by which I mean I have the kind of scientific comprehension pretty much everyone with a brain should have and be able to understand the universe around us. While there is no proof either way with respect to the claimed existence of deity, it is clear that something with no supporting evidence and no fit cannot be entertained as a reasonable concept. There are those who are satisfied that some explanations can justify the existence of gods, tears of milk on statues, the supposed conversion of bread and wine into flesh and blood to be eaten and so on. It is obvious, to me at least, that the Abrahamic god causes more problems for science/reason than it solves because, if "god dun it" becomes a reasonable explanation for anything, it cannot (once invoked/accepted) be logically opposed ... in effect, it would result in the collapse of science.

Other arguments to look up concern secular morality (I discuss this on my website), agnosticism vs atheism (the celestial teapot) and those things that are supposedly done in the name of atheism (the same article discusses Apartheid and Nazism which theists will often claim to be caused by atheism) which I am sure your opponents will claim.

There's a good link here, The Guardian: Is religion a force for good... or would we be happier without God? And typing "is religion a force for good" into YouTube brings up some good stuff especially the Stephen Fry vs Catholicism debate.

Please feel free to contact me again if it helps and to use my website (UKAtheist.org) and good luck :)