The tense standoff in Si Sa Ket on Saturday between a red-shirt mob and a Democrat Party rally deserves attention at high levels.
The red shirts gathered to protest against the appearance of opposition leader Abhisit Vejjajiva and other top Democrats.
But by mid-afternoon, the crowd was noisy, and then aggressive. The concept of free speech is sometimes difficult. But on Saturday at Sisaket Rajabhat University, the red-clad supporters of the government and the United Front for Democracy against Dictatorship (UDD) crossed the line.
While protest is clearly part of free speech, two acts by the red shirts are not. The first is making threats, and the other is preventing the free-speech rights of others.
The very presence of a crowd of red shirts at a Democrat meeting is a direct confrontation. But a crowd of 500 without leaders is not a protest - it is a mob. Large protests have clear limits of movement, with marshals and spokesmen. Mobs roam anywhere at will and make credible threats of violence.
That describes Saturday's actions by the red shirts at Si Sa Ket.
This is hardly the first time Mr Abhisit and his one-time deputy Suthep Thaugsuban have been met with mob action. In Ayutthaya last year, Mr Abhisit was pelted with water bottles by a similarly sinister gathering. The most frightening "protest" was four years ago, when red shirts forced Thai and foreign leaders to flee the Asean summit in Pattaya.
On that occasion, Mr Abhisit's car and bodyguards were attacked by mob members who posed real threats to the Democrat Party leader's life.
Some argue the Democrats should stay away from provinces and regions where red shirts are popular. They are wrong. The Democrats did not instigate Saturday's confrontation. If anything, they were too submissive. They tried to move their meeting 2km away from Sisaket Rajabhat University to a school.
It is fatuous to call the Democrats instigators. If the red shirts are so popular, and the Democrats so hated, what did the mob fear by letting the Democrats speak?
That is not to defend Mr Suthep's baiting of the crowd. Confronting a red-shirt mob on its own territory and calling its members "hooligans" in their home town is hardly a civil form of free speech. But it must be emphasised that Mr Suthep's words are free speech. They were provocative, but they were only words. Words have consequences, of course, and Mr Suthep deserves to be criticised.
This illustrates the truth about free speech that the red shirts have failed to grasp in every region of the country. The proper response to free speech - by the Democrats in this case - is more free speech. And while protest is an essential ingredient of free speech, threats and intimidation are not.
There are serious questions over why the police failed to provide the Democrats with their constitutional right to free speech. But the real question is where the UDD and Pheu Thai Party leaders stand on this basic human right.
As the red-shirt supporter and outspoken academic Somsak Jeamteerasakul said three years ago, the actions only make the red shirts look bad, while failing to advance any cause.
From Prime Minister Yingluck Shinawatra and her brother, de facto Pheu Thai leader Thaksin, on down, we should be hearing condemnation of such mob actions. Instead, we hear silence. That should change, and quickly.