|Clive Owen in Closer|
The short answer, in my opinion, is yes I think it's shady to meet up with an ex without telling your long term partner. The question I wish I could ask you is this: Why do you feel the need to talk about things/get closure/make peace with someone who treated you incredibly badly? Also, despite the fact that you are now in a happy, committed and real deal relationship, are you still holding onto the pain resulting from your ex's past actions? (Genuine question, not an accusation.)
The longer answer goes a little something like this: I'm going to go out on a limb and assume that your ex reached out to you, asking if he could apologise. To me, this could mean one of two things – first, and hopefully, he's genuinely sorry that he treated you badly and he would like the opportunity to apologise for his actions; secondly, and quite likely, he feels guilty and believes that apologising and justifying his actions will assuage that guilt.
I'm also going to go out on a limb and guess that if you are tempted to see him and you feel the need to make peace and get closure then you probably never got over the relationship. That seems like a pretty good reason to not go and see him behind your committed, long-haul partner's back, and I can see exactly why your committed, long-haul partner might not want this to happen.
One of the problems with cruel, manipulative men is that they know which buttons to press to get certain reactions, and they're not afraid to exploit situations to their advantage. What happens if you go to meet up with him and he says everything you ever wished he would say and you feel all these strong feelings and then he looks at you like he used to look at you and touches you like he used to touch you and then you suddenly find yourself in a situation where you might not be acting in the most monogamous of ways? That would assuredly be a gargantuan mistake.
On the other hand, maybe he'll straight up apologise for being a terrible boyfriend and behave himself appropriately like a gentleman. The thing is – why take the risk?
Regardless of all of the above, an email will surely suffice. He can write to you and tell you exactly why he felt the need to cheat or emotionally abuse you or humiliate you in front of your family or put his needs and wants and desires above yours at every step of the relationship. You can tell your current boyfriend that the email was sent and you'll be well within your rights if you don't want to share it with him. That way, you can sleep easy knowing you're not going behind your committed, long-haul partner's back.
I don't know for sure, but I'd imagine that there's a high likelihood that reading this email is not going to make you feel any better. I could be wrong, but isn't it just going to bring all those bad emotions flooding back?
My Mum said something very interesting to me the other day: Sometimes, when a situation is just too messy, there really isn't any way to make it better. Not every scenario has a fairytale ending – some things are best left behind.
For that reason, if I were you, despite the fact that I'd be dying of curiosity to hear exactly what he has to say for himself, I'd tell him thanks but no thanks. Say that you've moved on and you're quite happy leaving the past in the past. Be polite, say thank you for reaching out, but leave it at that. As far as I can see, you'll be saving yourself a whole lot of trouble.
Best of luck.
I LIKE YOU!