Why do you think all that? You can be an atheist and believe in leprechauns or trolls, nothing contradictory about that. Per definition. Saints, leprechauns, ghosts and trolls aren’t gods.
But you cannot believe Saints interact with God.
~Max
That’s true, but you can think someone is a saint without believing in any god.
Technically, yes, if sainthood does not depend on the existence of God. But empirically?
~Max
See, I’m as much of an atheist as they come by, but I think that Harry Belafonte was a saint (first person that came to mind). I don’t know what his spiritual believes were, but I think the things he did and stood for made him one, in a secular sense.
Arguably that is a different type of saint, with a lowercase ‘s’. To my point, you don’t pray to Harry Belafonte for earthly intervention, do you?
~Max
No, of course I don’t, and you’re right that this is a matter of definitions and semantics. So I drop it.
A Shinto worshiper would call all of those things, as well as what you and I would call gods, by the same word: Kami.
I myself would call them lesser gods - supernatural beings who interact with humans in some fashion. And anthropology backs me up: every god humanity believes in probably started as a local nature spirit or a beloved ancestor, with their story growing and evolving over the centuries. Trying to cordon off the “gods” section of the supernatural world is futile; it’s all religion, in one form or another. It’s all belief in something that can’t be proven to exist. The details are irrelevant.
That’s certainly possible. The atheist would just have to believe that the ancestor spirits could intervene directly, instead of by influencing some god. They could influence events when they were alive, after all. If they did still exist after death, why couldn’t they continue to do so? (In some senses, of course they do. Lots of people have acted either in agreement with or because of disagreement with the memory of what a parent or grandparent would have said about something.),
In theory you could have someone who believed that saints interacted with “God”, but that “God” wasn’t a real god but something else.
“God isn’t actually a god, he’s a parasitic alien worm that possesses people and flies around in a pyramid shaped spaceship. We’re gonna blow him up with some C4.”
Obviously, an atheist wouldn’t believe that saints intercede with God because an atheist has no belief in any gods. The rest of your question boils down to “can atheists believe in ghosts”, and sure, why not.
I’m sure lots of atheists follow lots of traditional practices. Atheist Jews I know still had a bris. But, obviously, the atheist in your example isn’t asking an ancestor spirit to intercede with gods that they have no belief in.
So, can atheists follow traditional practices? Sure, why not? Can atheists believe in ghosts (saints, ancestor spirits, whatever)? Sure, why not?
A good example of this is that atheists will often say “Oh God!” or “Jesus Christ!” – it’s purely cultural osmosis rather than indication of sincere belief. They’re basically words we say in certain situations. An atheistic Jew or even Christian who believe those identities or belief systems have more to offer than just theistic beliefs can consider themselves to be culturally Jewish or Christian or any other religious group, though the latter is pretty rare and the former much more common for complex sociological/historical reasons, but they’re both logically consistent. Almost no one would call themselves a Christian atheist, but there are plenty of (silent) atheists that participate in Christian culture and even go to church to be part of the community.
I celebrated Christmas back when there was enough of my family alive and nearby for it to be practical; not because I bought any of the mythology, but just because it was an excuse to get together with the family, exchange gifts, Christmas dinner and so on. So did my atheist aunt.
My parents were godless commies who took their atheism seriously. But they never did a hard push of any of their beliefs on us kids. Not only did we do Christmas and Thanksgiving, we did Easter - chocolate bunnies, colored eggs and big family meals. Because they wanted us to enjoy the normality of modern American cultural life while growing up. All of us ended up as easy-going liberal atheists (but not commies 
).
Years later I had a friend who had been brought up in a traditional religious household and then rebelled as an adult to become a very militant atheist. A dedicated attender of Chinese restaurants on Christmas, he was appalled my very atheist family always did traditional Christmas dinners.
My family’s holidays these days include people whose heritage is from at least three religious traditions; some of whom are atheists, some of whom are devout, some of whom are somewhere in the middle.
We’re celebrating various manifestations of love, joy, and connectedness. All of which, in our opinions, hold despite differences.
We did Easter and Thanksgiving too. I was pretty late in my teens before it actually connected with me that Easter was, technically a religious holiday instead of an excuse for Easter egg hunts, chocolate rabbits and baskets of assorted candy & knickknacks.
Me three. I was probably 12 when I noticed Easter had a religious component.
Lol, i was raised Jewish, but my mother hid chocolate eggs for us to find on Easter Sunday. We never did anything religious for Easter, of course.
My Mom used to get all bent out of shape because I celebrate Christmas and I’m an atheist. Bitch, please. Do you know how much of Christmas was culturally appropriated from other religious practices?
We celebrate a secular holiday. Sometimes my son asks me why this or that about Christmas. I try to explain Christianity to him, it makes no sense to him (because it doesn’t make sense) and on we go.
(“So this guy Jesus that lived two thousand years ago, some people believe he is God.”
“Why?”
“Because of… feelings. Er, well, faith. Some people believe in things that don’t have concrete proof.”
“Why?”
“Have I mentioned feelings?”
Silence. “How did he die?”
“Um. Badly.”)
Moderating:
The sidetrack on how many posters have enjoyed largely/completely secular versions of ostensibly religious holidays is lovely, but is a distraction from the OP. I think we have sufficient examples of @RitterSport’s and other assertations that atheists can easily follow traditional and cultural significant events without any actual belief, and more become a hijack. No warnings or serious concerns, but let’s get the debate back on track.