I think you are miss-characterizing these atheists.
It isn't that they believe in alien life-- it's just that looking at the odds to the best of our knowledge? It seems a likely hypothesis.
Vastly different from believe.
I'll be happy to use a capital G, just as soon as you manage to have your god show up in person.
Until then? It gets all the respect it deserves. Which is to say, none at all.
Now hang on there a second Bob,
Carlita's post clearly had the following;
"Do you understand the type of logic in this convo?
Also, I cannot prove god does not exist. He does not exist to begin with.
How do you prove god does not exist when he does not to begin with?"
The use of God here is as a name, much as I would use Thor, or Odin or the like, this is strengthened by the use of the phrase "He does not exist...". That's fine but when it is used as a singular, clearly in the context of a proper noun, a Capital is called for or a lesson in grammar for the clumsy English.
The author in this case is simply trying to insult the beliefs and intelligence of the audience.
Try replacing the god with toaster or the like and even you might be able to concede that the lower case 'g' is a subtle insult which atheists like to use but it doesn't work here. When you are talking singular about an entity that some-one believes exists by name, for example santa, panda or whatever, you respect that the object is a single definitive entity unless it is a group, as in the gods of Rome in which case the lower case is okay.
If you were referring to the Allah of Islam, would you drop the case for example? The poster in this case, might have correctly used the below, still sounds awkward but hey, I didn't want to muck about with other peoples posts too much.
Possible revision:
Also, I cannot prove the gods does not exist. They do not exist to begin with.
How do you prove gods do not exist when they do not to begin with?
"
I'll be happy to use a capital G, just as soon as you manage to have your god show up in person. "
I'm going to get back to my original idea here which was that hey, I know and count as friends a lot of really intelligent atheists. There is a sense that the odds favour life on other worlds but I would offer to you the same proof of God as you might offer of intelligent life elsewhere. Just because you think my understanding of the universe is wrong because it doesn't match yours, does not make you right. I cannot drop an angel at your feet and neither can you drop and alien at mine.