I'm thinking of painting graffiti all over the building tonight where no one will see
Why would you want to damage a building that way?
I think that I will feel freedom when I finish.
It is not right to vandalize a building to express yourself. Someone will have to spend more money to get it cleaned off and you could end up in jail or with a big fine. You should think about what you are doing and find another way to express yourself.
I put up the graffiti to protest my country. I don't think it's fair for me to have to support a country that I disagree with in so many ways.
You can express your discontent in graffiti by doing it in designated areas to put out your commentary. Taking it out on other people's property will only make them angry and not care to understand your point. If done in the right place, your artwork can last a long time and have an impact in your society.