with 'nothing after death', and 'universe starting without a god' being metaphysical explanations as well.

Uh, no? This is such a weird, confused argument. Atheism is simply the lack of belief in a god, which is the natural, intuitive stance to hold in the world we live in where there is no evidence of any gods. No "metaphysical explanations" required. Show me evidence of a god and I'll change my view, just like with everything else.

And humans are naturally spiritual

I mock people who bring up "human nature" arguments in any other circumstance, I don't know why it would be different here. You're not "naturally spiritual" you've been indoctrinated into a system of beliefs by people motivated by their material interests.

When the Catholic church was an important political power of the feudal societies, the revolutionary bourgeois developped criticism of religion to be able to separate politics from spirituality and claim the freedom to build a liberal capitalist society.

How is it now? On one hand you have far-right sects and religious orders that clench to reactionary ideas, but in the other you have billions of people who are oppressed by the imperial core and have been raised in a religious tradition. For a lot of people, like the Muslims in France, Islam is weaponized by the colonialist factions to demonize them. A lot of leftists fall for it. Outside of the imperial core, great parts of the masses won't listen to anyone who doesn't respect their religion because their religion is part of their culture, part of themselves.

My conclusion is : far-right religious factions must be dealt with because they are reactionary not because they are religious. Faith must be respected so that people aren't alienated from their culture. No organisation should ask religious people to renounce their faith as long as they are willing to use dialectical materialism and refrain from using scriptures to participate in debates.

I think that one philosopher said it best (paraphrasing because I'm no good at quotemining): in order to make religion less shitty, we need to do something about the shitty conditions that gave rise to it.

I don't think metaphysics is real though. The material world is all there is. When I say there is nothing after death, I mean that the chemistry inside your body that makes you alive stops functioning, and that's all that happens.

EDIT: to be clear, I'm not anti-religion. It's just that powerful people have a habit of using religious thinking for self-aggrandizement, shutting down criticism, and for justifying exploitation. It's not a coincidence that missionaries came hand in hand with colonizers

I'm an antitheist. If a god exists, it created evil and suffering and pain and must be made to answer for its crimes.

I'm an atheist but I think we should respect people's religious beliefs. If someone is a good socialist then it shouldn't matter if they are religious or not, being anti-religious will only make religious people avoid socialism for no real reason, we don't get anything by being anti-religious.

I mean, of course we shouldn't let religious institutions have power as they are usually quite reactionary, but the religious beliefs of people should be respected in my opinion.