I can, actually. I just don't find it necessary to correct everyone, like Talon said with the guy who told him wrong facts.. I find it sometimes rude to correct everyone on anything and this will only get you hated, even if you have good intentions.. However, online, it's a completely different story, you won't get hated for correcting someone or criticizing someone's idea..
I only correct, when someone corrects me and it his correction doesn't make sense (illogical).
I had a fight with one of the "popular girls" in the class, who started to fight with me, when I told her that a decimeter is longer than a meter..
I will still correct you, but only if necessary... And I don't usually participate in political/religious arguments, because people never admit their mistakes and at the end of the decimeter/meter argument, when she noticed how stupid she is, she told me to screw off.. So yeah, picking up fights with idiots will get you nothing.. This is the reason why I don't continue arguing with such people online, too. (Romario, eric, Alexei, Lord Mafia etc.)