We have an even bigger problem with definitions than previously mentioned.
In language, it's "usage" that always determines "meaning".
Dictionaries don't actually "determine" meaning, they just sort of "report" on meaning...
and even that is only good for a very limited time, as language is always changing.
So what was that about?
It means that not only do people have many different definitions of "nice guy",
but all of those definitions are EQUALLY VALID (unless we all agree on a specific definition).
So, if 10 people have 10 different definitions of "nice guy",
all of those definitions are equally valid, and I don't really get to yell at any of them!
(This isn't relativism, this is just how language works. Since "nice guy" is a common, pop culture kind of term, and not a "well defined technical term"... it's just NEVER going to have a clear meaning. BTW, this is the same reason many of our political debates on CC run off the rails.)
This is exactly why this same topic keeps coming up, and we keep having the exact same arguments.