Guys that are cheating on their girlfriend but act like their doing nothing wrong?

It's called being in a moral cesspool. Kinda like my old man, otherwise he was a very kind man, often was a cool dad (except when he would tell me as a kid I was too ugly to be his son lol), and rather well-liked by many. He sternly instilled values of honesty and honor in us, and ethics too. But when it came to keeping it in his pants, he was always cheating on my mom, he couldn't even begin to see he was doing wrong, even though we were living in a country where adultery was still a capital crime. And when my mom finally had enough and divorced him, he went with his current mistress, and SHE would ignore every suggestion he would cheat on her. She insisted she was special, different, she was to much WOMAN that she'd tame my old man. She didn't, and he cheated on her just as much as he did on my mom. And still saw nothing wrong with it either. And he married again, with a woman he was cheating on his second wife too. So far, according to my stepsister who's been watching him like a hawk, he's not cheated her yet. But then, age is catching up to him lol.

The right question is "are some people just really like this no matter who they are with..." since I don't think this issue is only found on males. But ask your question, yes, there are individuals that act like that, but why they do can wary. Maybe they are planning to dump their current partner and feel they can already get their "play field" going before it has happened, maybe they fear/think/know the person they are dating is cheating or is about to cheat on them so they feel they can do the same/make a "pre-emptive strike". Maybe they like the thrill that comes with cheating and don't actually care about their partner that much or maybe they have gotten bored of their partner in a sexual way and are trying out new things. Or maybe they just lack the same type of morals that condemn such actions or at least the will to uphold those morals. The possibilities are many and the only way to know is by getting an answer from the person himself/herself.