Brainwashed? erm yes.
Ok I have no recent direct experience of this, but this is what I have gleaned from MN.
If a man came on here and said, Met this girl, been with her a couple of months and she cheated on me... Worst case scenario (for her) Everyone would say Get Rid, Dump her.
Likewise if a woman came on here and said the same, she'd be told to get rid.
OK so you told him you had feelings at the time, but not the actual ins and outs (pardon the pun) He found that out later.
If he'd have posted on here asking what to do, the choice would be either:
A. Dump her
B. Ignore it, take into consideration the relationship since the discretion and choose to let it go.
to be clear
It would NEVER be
C. Hack into her email etc and spend months literally torturing her, finally working your way up to hitting her.
His months of torture (remember I have been there) have made you believe what you did was unforgivable. Only now years on am I able to see what 'H' did, he has not done it for years now, and the damage he did do, is now repaired, by me digging deep into my own self esteem reserves. This is what you must do, away from him, and you will find your lovely self again.
You made a mistake. So FFing what? he could have decided to accept it or not. If not, then walk away, not terrorise, not taunt and make you suffer!
Sweety, you will need a lot of healthy internal dialogue to get over the years of abusive conditioning you have suffered. There is nothing really that wrong with what you did.
The 'truth about you' is no more shocking or ugly than the truth about pretty much anyone.
Honey, you are out of this, you had a lucky escape.