Infidelity is a very interesting topic. I, for example, am in an open relationship with my long term bf of 9 years. Things are and always have been absolutely wonderful that said, if we weren't, and he cheated, I would likely not care simply due to the fact that we are young and its so common. It may be the psychologist in my talking, but I find the more educated a couple is, the more realistic they are able to be about expectations of each other. Open relationships may be common in the gay world, but in academia they are also rampant. While it had worked amazingly for me, I would never recommend it to another person without knowing their views on many things. I'm of the opinion that infidelity and love/respect in a relationship are not mutually exclusive things. That said, I would say that violence is not particularly forgiveable. There may be circumstances (over inebriation for example) which may allow a tiny bit of grey area, but in general it represents to me a person who you cannot trust (in the deepest sense, I find trust and infidelity superficial trust).