It's been a while since I've watched the episodes mentioned above, but I don't think it's fair to call Nick outright ignorant (hey, we can't let the tptb ruin the character
that easily). I was saying in another thread that Nick gives off the impression of being carefree and socially naive, so it's quick for him to make mistakes like that. However he is also sensitive and well-mannered, so he is always to accept criticism. And over the years, he has matured and become a lot more sophisticated in voicing his opinions.
The season 1 "ladies man" rep has been dropped long since. It makes sense to see it this way: we know Nick always wanted to distance himself from his family, possibly as a result of feeling overprotected as the youngest child. So as part of the distancing act, he tries out the frat boy, "multi-partner", womanizing lifestyle, which gave him his early reputation. After moving to Vegas and being on his own, however, he once again discovers his true self: sensitive, empathetic, and old-fashioned, thanks to his upbringing, and therefore decides that lifestyle is not for him. As he matures, he no longer feels the impulsive urge to deny his firm-rooted family values, b/c he has developed a secure and confident self-identity.
Whew...I wonder who my favourite CSI is? *eyes post*