It's quite an interesting concept to state it's black or white. Very little in life is black or white. I know people who are the absolute example of polite, but push them too far, you may be on the receiving end of their wrath. We all have a range of emotions for a reason.
I'm generally very polite and what you label as "nice" but there are also instances where I feel that people do take advantage of that when they view it as a point of weakness. I also know many people that are generally very brash, abrupt and rude and yet, get to know them and they are actually very nice people, they just prefer to be harsh at first glance.
First impressions may last for some, but I never judge people based solely off my first interaction with them as people are never one dimensional.
I agree, which is why I said so in my post.
This is in context to ignorance of facts you know, wasn't speaking generally. It's like excusing a lawyer for being rude to a client he/she assumes is guilty because he didn't know they weren't. I hope you catch my meaning, haha. I don't judge people based on first impressions either, so many things go wrong for so many people the first time around for anything.