It's one of those things that needs some balance. People seem to go to one extreme or the other. I have my opinions, but I try to stay open enough to accept that others do too as they are just as valid as mine or anyone else's. Often opinions will depend on circumstance. Something that might be morally unjust to me might be fine for someone who lives in a more dangerous situation.
As small communities the chances are we would all have the same values. However, internet puts us in touch with the whole world and we're not used to having people disagree with us. A flippant remark about Americans all being dumb comes from an outsider because they don't comprehend their differences in culture. I was reading an argument between an Irishman and an American and the American actually had more decorum and didn't rise to the insults being thrown at him and his culture by the Irishman.
So could we use more practise at keeping some opinions to ourselves? Absolutely! However, I think we could also use more practise at not taking insult from everything too. Either that, or go back to small communities.