Have you been living in a snow cave in the Antarctic for the last 10 years? Those "people with dissenting opinions" tend to be a pretty violent bunch. Leftists as a whole, tend to be much more violent than Conservatives. I will refer you to the archives for articles on the WTO/World Bank/IMF protests of recent years.
They think the same of us.
"Freepers are violent! I'm scared of that man with the mean look on his face!" - Hillary supporter.
"He that would make his own liberty secure, must guard even his enemy from oppression; for if he violates this duty, he establishes a precedent that will reach to himself."
- Thomas Paine