Do not play dumb. That statement makes perfect sense; it is referring to you trying to make a statement that you believe in and then saying that this is what society thinks to get away from your opinion. In that way, if someone says that you think that you will say that you do not, and if someone says you do not, then you will agree with them. It is a way to say something without worrying what you say. Society thinks you are a !@#$% retard, it told me so.
Decency is there and should be obvious to you. Would you ride a packed subway with a naked person next to you? It would violate your space, and it would violate the rights of others. It also exposes children to things that they should not be exposed to.
Since everyone is an American, they should be allowed to burn flags where they want, so long as it is not a fire hazard. By moving protest away, the government would in fact be nearly silencing it. Do you think TV crews would go to your house to see what you do there? No, that is a waste of time and would be dumb. If you want to physically protest the government, it helps to be at the government property.