Can Someone Explain This To Me?

I understand that the death of a 15 year old is tragic.

I understand that crowds may become unruly and angry at authority figures.

But -
Youth Riots in Greece Enter a Second Day
ATHENS — Youths angry over the killing of a teenager by the police took to the streets in Athens and other Greek cities for a second day on Sunday, burning shops, cars and businesses in the worst rioting in recent years.
OK, I've never understood this crap. how does burning shops and such ever help anything?

The violence continued despite swift action by the government, which charged a police officer with premeditated manslaughter in the shooting death of the 15-year-old on Saturday night. The country’s prime minister — whose government is already unpopular because of a series of corruption scandals — also wrote a letter of apology to the boy’s parents.
What are they apologizing for? You don't know anything yet. There has to be an investigation and trial. Talk about appeasement!

The youths regularly clash with the police, whom they view as symbols of the establishment. In most cases, the confrontations are relatively contained and end at the gates of universities with the young people holding off the police with gasoline bombs, rocks and slingshots.
But the speed with which the riots spread over the weekend — and the ferocity of the protests — seemed to take the government by surprise. The police nationwide were not put on alert until Sunday night — only after fires had destroyed dozens of businesses, including a high-end department store in central Athens.
*******Now here is the kicker for me.
Greek police and the military have been banned from college campuses since military tanks in 1973 rammed the gates of the school to quash a student uprising against the military junta at the time. At least 22 civilians died in that attack, which is marked every year by youth-led marches that occasionally turn violent.
What?? These hooligans are burning and looting and running amock and then they get to run into the university and they are off limits?

I've gotta be missing something here.