Do people deserve second chances?
Depends, I say.
On what? Well, that's up to you....
But for me.... There are plenty of things that will remove someone permanently from my list of friends, and my list of close friends, sex partners, and lovers is progressively more strict.
If a lover of mine commits a rape, do they deserve a second chance with me? Would I have sex with them again? Consider them as a close friend? A "regular" friend?
If a lover of mine commits a murder? Threatens me or a family member? Assaults or exploits a child? Peruses child pornography?
Those would strike people from my life permanently. No second chances. I think most rational people would agree.
So, what about "lesser" offenses? What if I overhear someone talking when they think that I'm asleep, and say something disparaging or exploitative about me (like, "Oh, V.A. is such a tease, I can't believe V.A. is withholding sex when obviously V.A. wants it and owes it to me"). Would that person deserve a second chance with me? Hell no. If they say to their significant other "Oh you should totally fuck the shit out of V.A.'s lover so V.A. leaves"? No second chance from me, nope. If they cheat on their best friend with their best friend's husband? Umm, no.
See, if someone is a *threat* to me or someone I love, I don't want them in my life. Ever.
As far as "just sex" goes, it's never "just sex", it's a bond of trust. By having sex with someone, you're trusting them to be honest and safe with you. You're trusting them not to pass you a disease without informing you that they have it. You're trusting them to use suitable birth control so that you don't reproduce unexpectedly. Especially as a man, you're trusting any woman you sleep with to act in a manner according to your mutually agreed-upon decision of what to do in the case of an unexpected pregnancy - and if she chooses to keep and raise an unexpected child when you don't want to, that's her right and prerogative. So you REALLY have to trust things like birth control, or you're stuck with the MOST major involvement possible to have in life, that of raising and rearing another human being. So, it's never "just sex". It's an extraordinary exercise in trust.
That said, I have sex with friends. I have "just sex" with "just friends". But NEVER, not EVER, with someone I don't trust completely. If the person gives me any indication that they do not deserve my trust, or, worse, if they actively have a *history* of damaged or misused trust, then, no, I don't have sex with them. I never place my health and well-being and future with someone I actively know is not worthy of my trust.
My point in all of this?
Polypenguin, you have other options. There ARE other fish in the proverbial sea. ESPECIALLY if what you want is "just sex", there are tons of people out there who are actually worthy of trust. Why settle for someone who you already know doesn't deserve your trust? Why not hop into some poly (or open/swinging, if that's more what you're after) discussion groups in the nearest major metropolitan area? Why not actively look for more people that are LIKE you, and also worthy of your trust?
Once you find more people that you CAN and DO trust, you'll look back at the people in your past that were not worthy of trust with a different perspective. Taking off the rose colored glasses is not easy, and sucks for a while, but OH MY GOD, is it ever rewarding. Take it from me.... I've been there, done that. Now, I look back, and I wonder why I wasted time on so-and-so, when I deserved SO much better, and I thank my lucky stars that I opened my eyes and found people who really DESERVE my time and love.