Proof religion is a cope

1. There are a lot of religions in the world. How is it reasonable to come to the conclusion that, based off of one scientific study, all of them are coping mechanisms?

The theory was proposed and then tested. That is how science works. I guess you could could come up with a way to test whether there are some which are  outliers, and then test it, but I am unaware of any such science experiment, and there is no reason to assume there is outliers. This proves that moralizing religions are a cope. As far as non moralizing ones, they probably have some sort of a concept of an afterlife, which would not even be included in the religion if it weren't for a fear of death and denial of it.

2. Wouldn't it be possible that some of them are coping mechanisms and others aren't?

Yes, it is also possible bigfoot exists.

3. Wouldn't it make just as much sense to say that the religions founded in harsher environments are coping mechanisms, but others might not be?

Sure, but we see anxiety is a reaction to harsh environments, so I would think that even religions in non harsh environments would probably have people who have a lot of existential or personal anxiety at odds with an otherwise easy society, will still more likely find god.

4. Wouldn't it be possible for one religion to be true and for the others to be coping mechanisms?

I guess, anything is possible.

5. Suppose that it was objectively and indisputably proven that every religion that has ever existed is a coping mechanism. Isn't it possible for something to be both true and a coping mechanism?

ofcourse. This is what disturbs me about the christians attacking this theory. They are ignoring the premises and just attacking the conclusions. These people are clearly using it as a coping mechanism, otherwise they would be able to point out that just because it is a reliable coping mechanism, it wouldn't necessarily make it untrue.

6. There are seven billion people in the world. Most of them follow a religion. Isn't it unreasonable to suppose that all of them have the same motivations for being religions? To clarify, wouldn't it be possible for some people to use a religion as a coping mechanism, but other people could be religious for different reasons?

Unlikely, though consciously they may rationalize a wide variety of reasons, Freud has shown us that human motivations when we remove people's rationalizations, is actually pretty narrow. We are motivated by a very tiny amount of things, which amount to sex and survival to sum it up. 

7. Suppose every single religion is a coping mechanism and every single religious person uses it as such. What does that prove? What actual consequences would that have?

If they come to understand such a thing, than they can rationally think about what would serve them better. An acceptance of death would have them adopting a more stoic or hedonistic approach to life. Either way they would be happier over all. If they refuse to just lay down and die, than humanity will be served because instead of coping with an inevitable death, they will be fighting it and possibly helping cure things like aging, which kills millions every year. I would rather these people fight death or accept death rather than just stick their head in the sand and pretend an afterlife exists.

8. Aren't painkillers, therapy, music, many or all leisure activities, and any number of things also coping mechanisms?

Not all coping mechanisms are bad. In the sense that I use cope with religion, I mean it to be a stand in for the phrase "Sticking your head in the sand". 

9. Suppose there is a true religion. Wouldn't it be reasonable to expect that it would reduce stress, so one would expect a true religion to act as a coping mechanism?

If people want to use it to reduce stress fine, but denial of death is harmful to themselves and society.

10. Doesn't everyone use coping mechanisms?

I'm just failing to see the point of proving that religion is a coping mechanism, and failing to see how this study can be generalized to all, or even most, religions and religious people. Even if it's true that religion is a cope, I don't see how that in any way invalidates it.