Tyrants are not bad people because they have power. They are bad people because they have no regard for others. They don't allow anyone to disagree with them. They use such power as is available to them to prevent disagreement from taking place and to punish it when it does happen.
Because of this, it needs to be understood that tyrants exist at all levels of human interaction. One need not be a head of state to be a tyrant. Simply being in a position to hurl insults can make one a tyrant, albeit an impotent one.
While a head of state tyrant will imprison or kill anyone who disagrees with him, petty tyrants are much less able to enforce their will on others. That does not, however, stop them from trying. Any attempt to force through threat or intimidation or verbal tirade another person to back down from their sincerely held views is an attempt at tyranny. This includes calling another person ignorant or uneducated or claiming that they have been listening to propaganda and don't think for themselves. It is a tactic employed to force compliance and is as evil as anything attempted by King George III against the freedom loving Americans who rebelled against his rule.
In order for a democracy to thrive, there must be room for disagreement. When we speak of freedom of speech, we are talking about the free exchange of ideas. This exchange is threatened when an honest expression is met by mean spirited insults, attacking the intelligence or education of the speaker in an attempt to bully them into silence. Such attempts at gaining tyrannical power over another are perhaps the greatest possible threat to freedom. And as with all forms of tyranny, must be met with the disdain it deserves.