And when, if, we do find life outside Earth...
Assuming of course, you're right about both life on other planets and about religions.
Maybe I'm being too optimistic here, but racism and hostility between groups of humans will cease, or atleast be greatly reduced in the event of finding intelligent alien life.
You're being too optimistic here. Very likely, we'll argue about it for a year, send out some radio signals that will take many thousands of years to reach their destination, and then after the novely wears off go back to our regular way of doing things.
Not to mention, in the age of Galileo, it was thought (due to christianity and a lack of technology) that EVERYTHING revolved around the Earth. As we know today, that is not true. It revolves around the Sun. The bible thumpers of the day stated that the everything revolves around the earth and they killed, tortured, or imprisoned anyone who disagreed with them through Science. Science prevailed.
And Galileo considered himself a Christian. Roman Catholic. The opposition to him was more church politics than "religion vs science." He didn't become an atheist AFAIK.
Also remember, just the act of discovering any life at all outside Earth, intelligent or not, is enough to send shockwaves throughout the religious communities.
It'll likely start with them putting it under a microscope and exhibiting extreme skepticism. Some may end up "shocked," others will simply modify their beliefs. In addition, many may not be affected at all: Not all religions (or even denominations within a religion) take a hard stance against ET life.
There is intelligent life out there. Its absolutely undeniable. There are more stars in the universe than grains of sand on all of earths beaches. Shear probability means there must be.
Sure it's deniable. One of the best arguments against life is the Anthropic Cosmological Principle, which claims that the probabilities against life appearing are far greater than the probabilities for appearing. Apply one of the cosmological equations, and you get a totally different result.
Problem is, we don't have a way to test any equation for validity. They're just wild guesses. The equation only hold up to logic insofar as it is valid. Unfortunately, there is no way to confirm its soundness.
validity = whether or not it has any contradictions
soundness = whether or not it reflects realiy
Logic may be valid but unsound by having premises that do not reflect reality.
For example, we have no way of knowing what fℓ is in Drake's equation. In fact, that and all of the remaining terms are nothing but wild guesses. If it happens to be an extremely low number, like 10-100, that itself could render life improbable enough to be pretty much impossible.
So right now the idea of alien life is totally outside the reach of science. I'm not saying it's true or false, just that our current science is simply not capable of saying anything about it.
If the aliens are about as advanced as we are, its going to lead to fear from both sides. which will probably end up leading to some kinda war that will end with one of us dead and the other mostly dead.
If the aliens are advanced as we are, if they are to launch a rocket today it will take about 18000 years to travel one light year. The nearest star (other than the Sun) is 4.2 light years away. You do the math.
It's very likely that (assuming other life exists) that if we are to be able to discover other aliens, it will not have any immediate effects.
For one thing, there is currently no faster than light communications and/or travel. Which will make it essentially one way communications. They are unlikely to even know we can hear them. And it's likely to stay that way for many thousands of years.
The science behind "faster than light" is pretty grim. Even the best theories are leaning towards "this is probably gonna end up being impossible, even for the most super advanced beings."
. . . and that's just the theoretical "is it even possible?" stuff. If you go from there to "is it feasible?" stuff it gets even worse.
So detection is one thing - but communication and trade are totally different. I think it's extremely unlikely we will be able to establich communication and/or trade soon after detection.