Fill the needs that religion provide for
The foundation of irreligious criticism is: Man makes religion, religion does not make man. Religion is, indeed, the self-consciousness and self-esteem of man who has either not yet won through to himself, or has already lost himself again. But man is no abstract being squatting outside the world. Man is the world of man – state, society. This state and this society produce religion, which is an inverted consciousness of the world, because they are an inverted world. Religion is the general theory of this world, its encyclopaedic compendium, its logic in popular form, its spiritual point d’honneur, its enthusiasm, its moral sanction, its solemn complement, and its universal basis of consolation and justification. It is the fantastic realization of the human essence since the human essence has not acquired any true reality. The struggle against religion is, therefore, indirectly the struggle against that world whose spiritual aroma is religion.
Religious suffering is, at one and the same time, the expression of real suffering and a protest against real suffering. Religion is the sigh of the oppressed creature, the heart of a heartless world, and the soul of soulless conditions. It is the opium of the people.
The abolition of religion as the illusory happiness of the people is the demand for their real happiness. To call on them to give up their illusions about their condition is to call on them to give up a condition that requires illusions. The criticism of religion is, therefore, in embryo, the criticism of that vale of tears of which religion is the halo.
Karl Marx — From the introduction to A Contribution to the Critique of Hegel's Philosophy of Right, 1844
This is a very difficult passage so I have highlighted the core. Religion is not merely pointless delusion; it fills certain needs that humans have.
- We ask difficult questions...
There are, of course, many problems connected with life of which some of the most popular are, “why are people born?”; “why do they die?”; and “why do they spend so much of the intervening time wearing digital watches?”
Douglas Adams, the Hitch Hiker's Guide to the Galaxy radio play, fit the fourth
We want to know how do the right thing towards one another.
What happens after we die? Is that really annihilation, or do some part of us and our loved ones continue on?
What are we supposed to do while alive, apart from surviving? Is there something we are meant to do?
What really happened at the start? How did life come about? How will it all end? What is beyond that which we can see?
Help, my child is dying, please save them!
If you want to defeat religion, you have to make sure you provide something better.
1. Revoke all religious privilege
Churches thrives mostly in part because they still enjoys privileges that few other organisations have. You need to fix this:
No state sponsorship
- Abolish the state church
- Make churches be opt-in, not opt-out
- No tax collection for the benefit of any church
- No tax breaks for churches
- Do not allow minors to be a member of any confessional. Entry into a congregation must be a conscious choice made by a consenting adult.
- Make everyone that has not entered the church by their own volition (such as on birth or by their parents) be non-members. If they want back in, they must apply for it, when they reach the age of full consent.
No legal privilege
No educational privilege
- Abolish religious instruction in school. Religion may not be taught as fact.
Enforce religious studies in schools, teaching about religions, as many as you can fit in. Teach about where the religions have gone wrong and encourage children to find logical errors and inconsistencies in the religious teachings and texts.
"Faith is not a virtue". Make it a "sin" to take things on faith, foster a spirit of science and enquiry.
Constitution of India, Part IVA, Fundamental duties, exerpt
It shall be the duty of every citizen of India —
- To develop the scientific temper, humanism and the spirit of inquiry and reform
Most importantly: enforce all of the above with the strictest of vigilance. Any hint, suggestion or argument against any of the above will be met with fierce opposition.
2. Challenge and undermine religious claims
Religions makes claims. All religions claim: "This is the way things are, this is how we should make them be, and here is how we and you should go about achieving that".
Break that down, all of it. Remove religion from the public discourse by harshly attacking any and all claims that stem from faith.
— We should permit [questionable practice]
— Why?
— We should do that because it is in accordance with the holy scripture and the divine will.
— No no no, if your deity wants to have a part in this debate, then they must bloody well come here and make the argument themselves! Not good enough.
And as it happens, there are lots and lots of people that love to tell people that they are wrong about things.

xkcd #386: Duty Calls
Endorse, aid and support any and all skeptical and religiously critical organisation you can find. Skeptics and humanists in particular. They will do a great job for you in undermining religion. Just give them a platform and you will get earnest and well read arguments against religious influence.
3. Become religion's best defender
This sounds paradoxical, but do consider that there are literally thousands of different denominations around the world. What you do is you say "We are not giving more or less privilege or hindrance to any one particular religion... all are equal. We will give everyone equal rights and equal protection".
First, this means that no denomination can claim that they are the bearers of The One Truth™. They cannot elbow their way ahead and claim more room than anyone else. They must all share the public attention equally. They cannot muscle their way over any other denomination.
Second, parody religions will sprout like weeds, highlighting the ridiculousness of religious practices.

Member of the Church of the Flying Spaghetti Monster wears official religious headdress on driver's license, as exempted for in Utah
With this you essentially reduce religion to be no better than people's bare opinion, since your choice of religion is a subjective, opinionated choice
4. Provide a better alternative
This is the hard part. What you have done above is just to take away religious influence. Now you need to fill the void with something else.
You must provide the following:
- A sense of community
- Non-religiously inspired ethics and morals
- Answers to hard questions
- Let "We do not know. We are working on finding that out" be an acceptable answer
- Effective healthcare that saves people from (apparent) certain death
- Comfort in times of anguish and sorrow
- Non-religious disaster aid, that outshines the religious counterparts
- Non-religious holidays, reasons for joyous celebration
- Non-religious culture
5. Believe
You need the believe that all of the above is done for the betterment of society. You are doing it for the people, for the children, for the weak and disadvantaged, for every citizen in your realm. Let it be indoctrinated into every person that holds an office of some sort; every into official that is in service of the state, that this is for the good of the people.
Finally... should this message be indoctrinated into the people? I would say: no. People tend to be stubborn and get into opposition of the people in authority say you should feel. So on the contrary: avoid making public pronouncements that your aggressive anti-theism is for their benefit, because that will just make them suspicious. Keep the indoctrination to the officials, and let the people just follow without knowing that this is what they are doing.