Yup. You don't change things by staying silent.

You've asked a lot of questions. Let's address them one by one.

Because property is such a sacred thing, right?
Who said property was sacred? What is important is that someone else put a lot of time and effort and sweat into buying that building. When you destroy someone's property you are making that property or business owner work even harder because you're too lazy to work to get your message out else wise. That's just being an asshole, not revolutionary.

Because spraying a stencil on the side of a building (which will probably get washed off anyway) is the same as spraying it on someone's baby, right?
Um, no. I didn't mention anything about assault or battery. I'm glad you've shown ignorance as to how paint works. It means that you've never destroyed someone else's property with graffiti. Paint doesn't wash off. You have to paint over it.

What about those people who don't believe in property?
We live in a country with laws. It's like that old saying with God, even if you don't believe in the laws, they still believe in you. Meaning, they still apply to you. And beyond the legal stance, I'll refer to my previous answer where the person who destroys another's property is not just taking away money, but making them work harder. Basically, being an asshat.

What about those that think everything in our community belongs to everyone?
Same answer as to the last question. We live in a country where property, by law, does not belong to everyone. And we live among those who do believe that property belongs to themselves, and again they work hard for it. I'd say the vast, vast majority of the world thinks the same. If you're interested in property theory, you should certainly check out Thomas Paine's work.

What about the Native Americans (or whichever country this was from) that originally lived on the land that building was built on; what do you think their opinion is on it?
I am Native American. You now know my opinion on it.

And what about those people that don't destroy property to get a message across? What about those who do it for something greater?
I'm not sure what you're implying here. If you're implying a pseudo-revolutionary thought, that the destruction of other people's stuff is the only way to make the country the way that you want? I'd say that that's one of three things: true revolution, terrorism, or childishness. For the overthrow of a government or society, you need a lot more people (say, a majority) for it to be valid. And even then you don't need to be graffiti painting to do it (the asshole theory), property damage should then only be collateral and unavoidable. Terrorism speaks for itself. As does being childish.