I will allow the bearded deity know as Carlin to answer this:

I don't know if I can pick just one!

That bunnies lay eggs. Ridiculous! We all know they come from the grocery store.

For me it’s the fact that a lot of people believe that ancient Jewish mythology is actual history.

I was going to agree with ricky gervasis and say the man in the sky !! another thing I don't understand is the dicotomy of them saying GOD is all forgiving and then say that they are a god fearing people. why would you fear your GOD. just boggles the mind.

The silliest thing for me is some of the advice religious people give. Like "God knows"..."Turn it over to Jesus"..."Hold on"..."God never makes a mistake" (yes He has according to scripture. Before Noah and the Flood, He, God repented that He had ever made man. Another one of my favorites is the belief that the Bible is the infallible Word Of God. Silly rabbit...it (the Bible) contradicts itself over and over again.

Prayer. The thinking that prayer can take the place of action or effort is asinine. The concept of worship to grant entry to heaven is questionable at best.
Devotion to one single ideology as supreme over others' beliefs as "one true god" is narrowminded as well. Why are cancer remission rates the same for people of all religions if yours is so real and true?
Also, rapture is absurd and irrational under any belief system and is a cult mentality.

I agree with all, but I’ll go with the idea that an all knowing creator of everything gives the least fuck about whether any individual passes a test, gets a green light, wins a sport, makes it through a speech without fumbling or any of the little things that people pray for and then assume the deity had anything to do with it regardless of the outcome.

The silliest thing is, a lot of religious people think the earth is flat!!! All science is fake, the moon landing was a scam, the sun is only 3000 miles away..... all because they are afraid to open the door to something in their "Holy Book" being wrong.

That an omnipotent, omniscient and "loving" god would knowingly create beings that were so faulty, he had to destroy the entire population of earth...including all the animals. And of course a flood of that size and duration would also kill every tree and plant. So basically god screwed up his first attempt at creation and had to start over. Then, he decided that his imperfect creations needed to suffer eternal damnation even though he'd have known in advance he was going to have to do that. What kind of sick game is that? I also find the idea of a walking, talking snake (before being condemned by god to crawl on his belly) a silly idea, God stopping the sun in the sky and another time moving it backwards in the sky rather preposterous. But such silliness is replete throughout the bible.

That because I am an atheist, I think murder is ok.

That everything in the Bible happened.

When people pray their team will win. Or that they'll win the lottery. They forget that if there's a god who answers prayers, what about all the other people praying the same thing?

People pray that a team wins over another. What a silly idea.

Prayer has to be the worlds biggest Copout. "Free Will" the world's biggest Excuse! The belief that the Bible is the inerrant word of god must be the worlds biggest delusion.

That their book says we're to take care of all the animals, and to eat them.

That there is a guy, wrapped in a towel and jumping from cloud to cloud -24 x 7- checking everything we do and judging / sentencing us according to our bad behavior.

Hilarious

That the bible and the canon of xian theology is divinely inspired, when in fact it was a lot of political debating.

I should have said most flat earthers are religious, not that most religious people believe in a flat earth.

If prayers do work why hasn't disease been completely vanquished? Actually I did pray for tht as a Christian so I know its been done. So now the classical answer is "Its God's will." If this is the case than our free will means nothing...The endless circles of theology...

This video captures the essence of the silliest aspect of belief, to me...

That I'm a witch because I own cats and volunteer with animal rescue groups. Getting tired of death threats and finding anti-hex stuff on my doorstep.

"Burning in hell."

I think believing that there is a spirit somewhere who takes a personal interest in everything that you do, is pretty silly. Consider how many people there are in our world. It sure would be difficult for him/her.