The shaming tactic crops up in many areas of life from relationships between two people where one partner may attempt to achieve leverage over the other by comparing them unfavourably with an acquaintance or exemplar of an assumed ideal. There are culture wide examples too like the recruiting poster with a little girl at her fathers knee asking " what did you do in the war daddy ? "
I have never been asked if i am ashamed to be an atheist, but i have been told directly i am wrong in my world view and have had a few "discussions" that have usually gone nowhere.
I don't tolerate religious people offloading on me expecting i will politely obey an assumed social norm and respect their nonsense without any comeback.
One or two have conceded i know more about their religion and history than they do.
I have learned to cull a lot of the waffle and " cut to the chase " as the saying goes. I arrive at stalemate after one or two laps instead of fifty. As is a very common experience , it usually ends up with me pointing out there is nothing objectively self evident to support their claims and they, devoid of any explanatory output, pronounce upon the necessity for faith and my woeful lack of it.
I tend to avoid such interactions as a waste of time as i have grown older.

I just tell them I'm too stupid to believe in talking donkeys, magic fruit and a man live inside a fish for three days. And if they asked me if I was ashamed I would tell them that I am too stupid to be ashamed of it.

Go Ask Jimmy Swaggert, Joel Olsteen, Joyce Meyer and Pat Robertson if they are as Christian as they supposedly try and make themselves on the Media. Then go and look up the definiton of a Fraudulent, Deceptive Conniver who places Rich Estates, Private Jets, and Media Brainwashing as the road to salvation.

I'm more agnostic that atheist. A few weeks ago my cousin tried to out me on FB by starting a comment with "I know you don't believe in God. . . Because her mom shared a meme supporting saying the pledge of allegiance in public schools. All I said was I agreed with SCOTUS not allowing the pledge. Boy, did I hear how negative I was. She told me if I didn't have anything positive to say I should just move along. I blocked her immediately because I just didn't want to hear her holier than thou hypocritical attitude. Yes, I can be snarky but I am really funny. The whole family knows how religious she is. And, like me they avoid talking about religion.

Literal conversation I had last week with a co-worker:
Them: I could never trust someone who doesn't believe in God
Me: do you trust me?
Them: of course, why?
Me: because I don't believe in any gods, yours included.
Them: then I can't trust you anymore.
Me: the only thing that's changed in the last five seconds was you closing off part of your mind and heart to me for no reason. I'm the same person I was before you knew about my lack of belief. I haven't changed, you have. And not for the better.
Them: I... I mean...
Me: save it. I don't care. Your image in my mind has now been forever changed for the worse. Good job. Bye now.
And I walked away...

I still don't understand the hostility directed towards people who simply don't believe. It puzzles me.

I don't bring it up unless asked directly but:
Catholics and Anglicans are either curious or repelled by it
Muslims tend to either be confused or appalled and say it is impossible
Hindus tell me I have not found the right god yet
Buddhists tell me that is my way
Baptists get angry
Methodist throw water at me and
Jews just tell me no I'm not I'm attention seeking.

I know folks who can't resist having a dig at my atheism. And the most vocal critic is a woman who years ago, after a couple of years chatting online, wanted to leave her husband, also a friend, and come over to live with me. Had to be really firm about that not ever happening. They are still together and ardent churchgoers, full of christian feeling. Just goes to show they aint perfect, even if they are 'forgiven'. But i just can't understand that mindset; using piety as a weapon and the perception of forgiveness as an excuse.

I'm not shy about it, but I also don't tend to talk about religion, or my lack of it, with most people. I'd rather not hear about their religion, and don't assume they want to hear about my disbelief. it usually works well. The rare instances where it's been pushed, I ask very uncomfortable questions until they stop.

Nope! I'm an out and proud atheist and nobody has ever suggested I hide it. Most people respect my spiritual views. Those who don't can avoid me. I have avoided gatherings I know will be religious, as they just don't interest me. But if I'm caught somewhere there is praying, I generally keep respectably quiet, without being asked to. That has never happened!

I haven't been ashamed, or made to feel ashamed. I'm proud to be an atheist, but I'm not loud about it. If it comes up naturally, or if someone asks about it, I am more than willing to talk about it. I'm not expected to keep it quiet, and if someone does, I do my best to distance myself from that person. I haven't had anyone avoid me, and luckily I haven't had to avoid anyone.

Not so much. I've had several people very confused by my atheism. Why would you not believe/love God? Or do you worship the devil? How can you do that? Mostly never occurred to them. Also, if they hear me out, they generally are less confused. Not always but I try to be persuasive. ?

Never once have I been asked those questions.

I am not that overtly "out". I don't conceal my beliefs but I don't trumpet them either. The topic mostly doesn't come up, and that's fine; life consists of a great deal more than what I do or don't afford belief to on a particular topic that most people don't want to discuss outside their private clubs to begin with.

In those places where it's appropriate to discuss these matters and people wish to discuss them (mostly, places like this and similar sites) I've experienced all the things you describe but it doesn't disturb me.

If I had family or an employer hectoring me to conform (fortunately, I have never had that problem) I'm sure I'd experience all those gambits there as well. And there would probably be some family members who would ostracize me and I might lose my job and so forth. In practice though I find that so long as you're not a dick about it, those things are actually pretty rare. And the bonds of such relationships are stronger than ideology if they are even worth keeping.

Although there are certainly exceptions, because "people of faith" are mostly, it seems, people of weak faith, considering how violated and threatened they feel and the degree to which they abreact to even passive lack of endorsement for their view.

Never.

I don't talk about my Agnosticism and I don't hide it and was never embarrassed if anybody knew I was.

Never and no one can intimidate me on any of my beliefs.. I care deeply for people but I don’t give a shit about what people think of me or my intellect, thoughts, beliefs, opinions

I have had theists tell me they feel sorry for me. How condescending can one get? There is no hate like christian love.

Very comfortable in my own skin. Being honest about who you are is pretty important. If they are truly well-thought-out beliefs that you feel strongly about I don't see any reason to be ashamed or silent. Being confident and comfortable without being confrontational seems to work well for me.