I’m a cheater and no I can’t stop, I’m finally happy. I won’t do it in my next relationship as I no longer believe in monogamy so I will be upfront and honest about it.

In the case of my ex husband- yes. He has cheated before, during and after me.
But I don't believe that everyone can be put in the same box.

Depends on the person and situation really. I cheated on an ex of mine. I had suffered a miscarriage and tried to break up with him. I did it face to face, over text, tried to get his mates to help me out (they did, he wouldn't listen to them) I even had the police remove him from my house when he was outside banging on the door begging me to let him in. He would still message me that he loved me and wasn't going to let me leave him. As a final resort I cheated and made sure I would be caught. Nothing. He cried and did a whole "you're just in a bad place now, we can work this out." He FINALLY gave up when he met someone else. I felt at the time that it was the only thing to make him see I didn't want to be with him, but even that didn't work. My kids father, on the other hand, is a serial cheater. When we got together it was all his ex's had cheated on him and he was the victim. Yeah I know, that should have been my first clue. After he cheated on me, I found out he had cheated on every one of them, and has had 2 relationships since me and cheated on them as well. He is one that I believe will never change.

No not at all.
I think it’s a projection of peoples feelings who think that about someone.

If I did think that than I just think that nobody is any better than their worst self and incapable of change.

Will a drug addict always use drugs?
Will an alcoholic always drink?
Someone who told a lie never be capable of telling the truth thereafter?
Someone who argues and nags in one relationship continue to forever argue and nag.
Someone who’s insecure always be insecure?
Someone who yells at their kids incapable of speaking to them with respect?

No. We are never incapable of not repeating mistakes.

It’s a ridiculous concept.
Once a cheater always a cheater. And know many cases that say it to be untrue.

Yes. They put their desires ahead of their relationship and family. By rubbing your privates against someone else you've destroyed a family. Selfishness on an epic scale. No trust for someone who could do that, they will do it again.

To cheat you would either have a. a shit moral compass or b. excuse your behaviour to yourself or c. Lack of judgement about the situation, your own sense of control or else your thought patterns. Regardless of who/what/where ... if you did it once ... the odds of doing it again increase exponentially. However, if it was a once off one time thing (one night stand type) and it left you with a horrible sense of guilt and terrible consequences it may prevent you from ever doing it again.

Yes