Religious people are [clever|stupid]
Athiests do not "know" that god does not exist (unless they are not very logical), they might be pretty sure, confident or just consider it unlikely.
Agnostics are fence-sitters, it's actually takes a significant degree of faith to think that in the absence of any provable, repeatable evidence it's close to 50/50 that god exists, by definition agnostics are people with a lot of faith, around 50% (although, I suspect that most agnostics are in reality Pascal wager atheists - which is odd because if there is a god [he|it|she] knows what you really believe, so there's actually no point in pretending).
Theists believe there is a god, in the absence of any provable, repeatable evidence which means they either right (clever, if they got the right god) or wrong (stupid, if they wasted their life worshiping nothing, or worse making other peoples lives worse because of it).
Exactly the same prinicples follow for belief in aliens;
There might be aliens - but I can't prove it or communicate with them, if they do exist they are probably too far away to reach us so it's not worth living my life like there is aliens.
It's 50/50, I won't commit to belief or otherwise, I'm just as happy to believe in aliens as not to believe in aliens, no point in asking my opinion about them, I have nothing to say (although I might spend a lot of time saying nothing).
Aliens exist, theres no repeatable proof, but lots of hearsay and things I can't personally explain, so it must be aliens, I will make important life decisions on the basis of aliens existing.
So, now for a summary - these beliefs are so close, there really is no "in principle" difference believing in god or believing in aliens, imagine a world where people kill each other because of what different peoples thought their aliens told them, or what about spending two hours every week singing praises to your particular alien - does this make sense?
People have great capacity for caring for their fellow kind, this capacity does not come from aliens|god it comes from humanity, redirect the "love" we feel for aliens|god at people (because that's where you really feel it) and the world will be a better place, if you don't believe me just spend one day (16 waking hours) smiling and being nice to (almost*) everybody you meet and see if you have a better day than whe you do worshipping your alien|god of choice.
*even tramps that smell of wee, unless they acost you