Sarah, I feel bad for you, I really do. Some of these threads can get NASTY.
I don't have an answer for you. My best guess is that those people, who habitually antagonize, belittle, personally attack, etc are just plain mean, or simply, reacted before thinking.
Not all nurses are this way, as not all people are this way. This person, if not a RN belittling an LPN, would be a grocery store clerk belittling the stock boy. Unfortunately, it's human nature. I think Brownie in one of her posts, I think way back in the dreaded "why LPN" thread, went into why she thinks people do this, and how she copes with it: considering the source, etc. Maybe go back and dig up the dead, so to speak, and see if you can find her post.
I wish you luck Sarah, in your nursing career.