I said they "wouldn't be too happy about it". This could be them indirectly being unhappy about the flag burning or directly. Their decision to get this guy might be because it had some negative effect on the people (which is the cause of their unhappy feeling).
It's not. The flag is a metephoric symbol of the country. You respect the flag because you respect the county. Buy defiling the flag, you are showing your disrespect for the country.