It is regular thugs — sent by officials, secret police, mafia bosses, or persons taking more than one of those positions — who smash windows 9 times out of 10. However, your logic takes unwarranted turn to “power of propaganda” and “people of Russia”, probably because there's plenty of stereotypes of how “people” in any country behave to use.
Nah. You'll more likely get your window smashed if you gonna put some Z-swastika on it. No doubt a lot of population in Russian affected by propoganda, but primary goal of Putin's propoganda is to make people passive and not to have opinion on anything at all.
But yeah if you put anything Ukraine-related or anti-war related police will come to you immediately.