A “Protester” is someone availing themselves of their First Amendment rights. In Ferguson, you may not agree with what they say, but their right to peacefully assemble and express their grievances comes well before your specific issue with their cause.
A “Looter” is someone who believes they are entitled to destroy or steal property, because they are “angry,” or for some other trigger. No one, no matter how angry nor no matter the cause of their anger (including the killing of Michael Brown by Ferguson PD Officer Darren Wilson,) has the right to take or destroy what is not rightfully theirs.
In short, Protesters should expect our support. Looters should expect to get shot.