Well, it's just a matter of defining "nice" in the context.
If your brother tells you about some teacher beeing an ass-hat, and you find it nice to know, then it is nice.
If you hold a gun to someones head and tells them you'll blow their brains out if they try to fuck with you again, it's still nicer than just blowing tehir brains out without giving them a chance to prevent it.
If you tell the grumpy biker he looks tlike a douche in his gang vest, he gets pissed and you gets punched, and no-one benefits, so it's not really nice, for anyone.
If you tell people about how this big corp is fucking up the shore by pumping toxic waste into the ocean, you're not beeing nice to them, but you're beeing nice to everyone esle, even though it's unpleasant news, ti's ebtter to know about it than not to.
If you tell people that they're ass-holes (and you judge that the consequences are not bad for you) cause they piss you off, and you fell better after having stood up to them, you did something nice for yourself.
These are just a few examples.
Nice is not an objective word with a universal meaning, it's situational.
That would be the best way for me to explain teh saying, and somewhat mold it into something usefull, but in the end, it's just a stupid saying.
If your brother tells you about some teacher beeing an ass-hat, and you find it nice to know, then it is nice.
If you hold a gun to someones head and tells them you'll blow their brains out if they try to fuck with you again, it's still nicer than just blowing tehir brains out without giving them a chance to prevent it.
If you tell the grumpy biker he looks tlike a douche in his gang vest, he gets pissed and you gets punched, and no-one benefits, so it's not really nice, for anyone.
If you tell people about how this big corp is fucking up the shore by pumping toxic waste into the ocean, you're not beeing nice to them, but you're beeing nice to everyone esle, even though it's unpleasant news, ti's ebtter to know about it than not to.
If you tell people that they're ass-holes (and you judge that the consequences are not bad for you) cause they piss you off, and you fell better after having stood up to them, you did something nice for yourself.
These are just a few examples.
Nice is not an objective word with a universal meaning, it's situational.
That would be the best way for me to explain teh saying, and somewhat mold it into something usefull, but in the end, it's just a stupid saying.