trying to spread aetheism/discourage theism is immoral

My opponents argument rests on whether theists are happy, but whether religion makes a person happy does not have a bearing on the moral issue, as I will show.There are many religions, mostly mutually exclusive, so most of them must be false. There is no information that conclusively makes the case that a god exists: Ultimately belief must be a matter of faith. Billions of people must be in error believing in the god they do. Since it arrives at different, mutually exclusive, conclusions, faith is not a reliable means of arriving at truth.If we do not encourage people to abandon an unreliable means of arriving at truth, we leave them prone to error, to have incorrect information. Obviously we value correct information, not just because of the survival value, but of its own sake. Ceteris paribus, it is self-evident that we have a moral duty to do what we can to ensure our brothers and sisters have reliable methods for arriving at truth. Furthermore, it is obviously to the benefit of a society if our methods of arriving at truth are reliable. We can do much with factual information. So it is moral to try to create a culture where only methods of reliably arriving at truth are used.Now obviously atheists think all theist beliefs are false. There is an argument that we should leave people to their beliefs if it comforts them or makes them happy in some other way. However, very few people would like to be patronised in this way. I personally would not like to be left with an erroneous belief just because it made me happy, so how can I in good conscience think it is moral to treat others in this way? From the atheist's point of view, to try to discourage theism is in fact the only moral option. Given that most theist beliefs must be false (mutually exclusive religions), from a utilitarian point of view the atheist is morally right to discourage theism. By discouraging theism, the non-believer is discouraging a false belief at least most of the time.The non-believer has a moral duty to speak up against any perceived immorality. Perhaps the believer may find ways to reconcile or mitigate the perceived immorality, but the non-believer provides an important service in putting religious ideas to the test.‘If a man has sexual relations with a man as one does with a woman, both of them have done what is detestable. They are to be put to death; their blood will be on their own heads.'[1] 'Anyone who steals must certainly make restitution, but if they have nothing, they must be sold to pay for their theft.'[2]'Men have authority over women because God has made the one superior to the other, and because they spend their wealth to maintain them. Good women are obedient. They guard their unseen parts because God has guarded them. As for those from whom you fear disobedience, admonish them and forsake them in beds apart, and beat them.' [3]The religious texts these statements come from are held to be authorities, but the non-believer can in free conscience assess such sayings purely on their merits, without regard to their authority.Assessed purely on the merits of its content, the edict against homosexuality is extreme for a victimless consensual act between two adults.Assessed purely on the merits of its content, the condoning of slavery is contrary to the principles of basic equality that democracy espouses. It is also contrary to our modern conceptions of human rights. It denies a group of humans autonomy. I have no hesitation in saying that is immoral.Assessed purely on the merits of it content, the verse enjoining men to beat disobedient women is despicable to those who value an equal and just society.These tenets are anathema to principles, and moral principles, we hold dear. Is it immoral to speak up against these tenets? The non-believer can provide an important moral challenge to the believer.There is a more fundamental issue here. It is the very principle that all ideas are subject to scrutiny and examination.Religion can tend to obstruct this principle, by the notion that some ideas should be held sacred.By testing ideas without restriction we can see what works, what accords to our moral intuitions, what needs to be changed. The non-believer, by not holding any ideas sacred, can help prevent moral stagnation.Planes do crashOn my opponent's "planes don't crash" analogy:The correct analogy to religion would be if an airline told everyone that planes couldn't crash. This is immoral. The only moral choice for someone who is aware that planes can crash is to make sure other people are aware of this fact, so they can make informed decisions about whether or not to use air travel. My opponent, who fully accepts that religions may not be true, would have it that people were lied to, so as to prevent informed decisions. This is immoral.[1] Leviticus 20:13[2] Exodus 22:2-3[3] Quran 4:34