What We "Know" And What We Really Know

Why is it that people try to start things or ruin things with information that they think they know. I mean, if you really really want to start something make sure your info is 100% accurate so that what you are saying doesn't come back and bite you in the butt. Also, if you are really trying to end something, again make sure your information is right. This goes mainly for the people who are REALLY supposed to know EVERYTHING about someone, and then you get a message that is the biggest and fattest lie on earth, and they believe every word of it. It seems so silly to me personally. Mainly for the fact that it is the stupidest thing ever and it kind pisses me off because this is where rumors get started and this is where peoples lives get fucked up. It has happened to me countless times and it has happened to other people i care about as well. Its just stupid crap like this that kinda makes me want to punch people. Sigh...