What argument could you make that flag burning is likely to cause violence and
therefore should be against the law?

Flag is the national symbol of a state, organization or office. It represent the dignity of such body and should be honored.

Burning a flag is a national disgrace and a total letdown to such body and should be a huge crime against the law. Committing this act should attract a sever punishment to set ahead of those intending to tow same lane in the nearest future.

the use of electrical signals that transit messages is know as