B’s got a role, but we don’t have enough information to know exactly what role. You don’t cheat on your spouse if your relationship is in good shape.
Perhaps, but A could have always opted for divorce rather than infidelity. As long as there is no bar to leaving the relationship, there’s no excuse for violating the rules of that relationship.
I don’t know that this is necessarily true. Some people are just non-monogomous by choice or nature. B could be the perfect spouse, but if A is a cheat it won’t make a bit of difference. Any relationship A is in would therefore be “bad” by default, but not due to any dynamic between A/B.
I would have to agree with this part, at least. It’s A’s fault predominantly, but partners do not exist in a void.
C is a opportunist. As such, there are lots of opportunists in the world. A good and moral personal rule is, “Don’t sleep with a married person if they are not married to you,” but unfortunately there are thousands of married people willing to do so.
Not necessarily true. Some of us can be great partners but find out the hard way that the person who promised undying love and fidelity is a complete asshole who can’t keep his/her pants on if they get so much as winked at by another. Hmmmph.
I blame genetics for not hardwiring people for monogamy and poor impulse control for breaking social convention.
I don’t blame C much, unless C knows B, then everything changes. If C knows B, C is much more to blame. Not quite sure why this makes a difference to me, but it does.
B is to blame because she has been really cold since the incident at the Christmas party and she doesn’t understand how hard it is to hang on to a job in this field at the moment and I’d like to go out with my friends every night like she does but I have to put in the long hours and sometimes it seems like I’m just a boarder at home except that I get criticised more and I’m too tired and she just isn’t interested and the bloody kids act like I’m a stranger and no matter how much of my weekend that isn’t long enough I waste doing stuff around the home it isn’t enough no not nearly enough and C doesn’t lay all this shit on me and she is really a nice girl who is warm and giving and I just wanted some companionship.
So all things considered I blame B.
Does anything change (other than the severity) if this is not a marriage, but just a relationship? I have, (please don’t hate me) been Mr. C, but only in with regards to high school flings, not marriages. Am I still a dispicable bastard? I should point out that with regards to my previous post, I did not know fellow B, which somehow made it better in my mind. Certainly better than if I had been friends with B, at least.
The blame goes to A. C may not be the salt of the earth, but the relationship and commitment is A’s responsibility.
A = C = to blame.
A, for breaking A’s promises. It doesn’t really matter to me what B did (or didn’t) do. A made a promise. A willfully violated said promise. If A were interested in behaving in a fashion that breaks A’s promise, then A is free to seek release from A’s promises via divorce. Or even legal separation - I’ll go legal separation.
C for HELPING A break A’s promise. C is aware that A is involved, and proceeds regardless.
Both are engaged in wrong behavior. Both are aware of the fact that their behavior is somewhat less than exemplary.
If I were forced to pick a winner in the “Who’s A Bigger Asshole” sweepstakes, it would have to be A, but they’re both behaving badly.
I beg your pardon but who gave you permission to report the recent events of my life? 
- A broke a promise and is morally culpable.
- No matter what B did, it does not justify cheating. B may have done some evil stuff, but two wrongs. . .
- Hi Opal!
- C’s culpability is a little more complicated. I think it is a shitty thing to do to disrespect commitments made by another person. The law used to recognize causes of action for alienation of affections and seduction (and apparently, in Utah, it still does) but because they were based on the notion that the wife was the husband’s property, most states got rid of them. I propose a two pronged approach instead:
I. Like interference for contractual relations, an actor is morally culpable for a fling with a married person if the actor’s actions were at least partially malicious.
II. If an actor has sex with a married person, knowing that the person is married, the actor can then not complain if the actor’s spouse (or future spouse) has a fling or flings.
Now there’s the conceptual and abstract consideration of this generic moral/ethical situation that this post was looking for…
It depends. Has B let him/herself go?
A & C are both at fault in your scenario.
If A had NOT told C, then C is operating in good faith on the assumption that A is unattached. But the minute A tells C that he’s married, C should drop him like a hot rock.
Me too. 
I’d be interested in knowing what kind of gender assignment people were giving to my letters, as well as how, if at all, their opinions would change if the roles were reversed (e.g. poster assigns wife as cheater but, in reality, it was the husband; A and C are straight v. gay (which I hadn’t even considered until now)). I considered asking all of this in my OP but chose not to because I’m not sure it matters.
This isn’t based on any kind of real life situation, so I haven’t considered B’s involvement. Maybe B works really hard and so they’re tired all the time. Maybe B doesn’t pull their weight around the house and A resents having to clean up after everybody all the time (I don’t know if they have kids, either. Let’s say “no”.) Maybe B is selfish in the sack. Maybe B is perfectly fine and A is just an asshole.
Also, C doesn’t know B because, I dunno, B prefers jogging and biking to gym membership or something.
On preview, UrbanChic (and anyone else), does it really matter? I’m going to say no, B hasn’t let go. Sure, B isn’t as young as they used to be, but they try to look good. Even if B gained 57 pounds and wears nothing but sweatpants and nasty old t-shirts with BBQ sauce stains all over, would that justify A being a cheater? Why not just leave B? Or, heaven forbid, address the issue and try to fix it?
As said by others, B may be partly to blame, but C was not part of the vows made between AB, C is pursuing C’s happiness. A is the one that should get A’s ass kicked.
My initial post was just my lame attempt at humor.
*Ew!
C is 100% blameless in the breaking of A’s marriage vows. A made the vows, A made the decision to break those vows. If all the C’s in the world conspired to not have sex with A, that would just be a technicality. It wouldn’t change the fact that A didn’t respect his/her marriage vows.
C is guilty of having sex with a bad person. As a general rule of thumb, I don’t think one should have sex with bad people. That doesn’t make you responsible for their bad deeds, though.