The power felt when realizing that there was nothing out there that was going to strike me down for what I felt, or thought, was extreme. And before thinking, some of the most valued people in my life were alienated by my words and actions. Since then I came to realize that it was the insidiousness of religion that I found evil, not necessarly the people that were caught in the practice. Try placing your anger and resentment toward the positive rather than the negitive and instead of passively lying in wait, choose to invision how you would want to be as a happy, non-monster, person that doesn't believe in gods. If you were a true monster, there would be no question.

Why would you feel a need to be "vicious"??? Religious beliefs are just one tiny factor in true friendships.......

This can cut both ways. My wife is not shy but let's just say withheld and slow to make friends, so when she moved to a new area she was delighted that a colleague strongly pursued her and wanted to be her BFF. My wife is atheistic and liberal and her friend was religious and conservative but that never got in the way. Until my wife divorced her 1st husband. Then her "BFF" pulled back and stopped having anything to do with her. It wasn't explicitly laid out like you describe but it was clear that my wife had violated her friend's divorce taboo and since my wife's ex wasn't abusive or cheating there wasn't a sufficient justification for it. So my wife went from hero to zero in about 10 seconds. So much for the concept of BFF.

Was my wife's friend a monster? No, but she was not sufficiently committed to the friendship to discuss / work out any issue and to see my wife's humanity even if she did something that she wouldn't particularly approve of.

So I doubt you're a monster but it IS rather monstROUS to "turn on" your friends for life, and you're right, however belatedly, in seeing it as a poor hill to choose to die on. It may well have been that some or all of these would shut you out in their own right, and maybe you sensed this and it was your way of avoiding that with a preemptive strike. But that should have been on them, instead of you giving them an excuse to do it.

So my thought would be, just don't make that mistake again and be man enough to go back to them and apologize for being an asshat about it. They may or may not be willing to repair the relationship and you may or may not care at this point, but it's the right thing to do.

Be ready though for them to mistake this as an opportunity to win you back to the fold. You should be careful to present it as, I don't feel I was wrong to leave the faith, but I handled it badly and ill treated you and I'm apologizing for that.

Sounds about right to me..when my Haiti MK (missionary kid) childhood friends and many of my relatives began posting hateful racist, and anti-LGBTQ memes during the 2016 election, I began defriending/blocking them.

I also quit contacting them for good.

Are you looking for approval or forgiveness for your actions?
This isn't the confessional.....you don't get absolution here.
Only you can decide who stays in your life and who gets removed.
Those choices -- and consequences -- are yours alone.

Atheism isn't really a dogma that requires sacrifice from a non-believer.

This is light on details but ...

One of the biggest mistakes atheists, especially anti-theists, make is believing theists are inherently less intelligent.

If you care about your friends, don't toss them aside or think them less because they believe. Heck, one of the principle rules of new Satanism is "don't be a dick."