Mr. Donovan is speaking of rules. A boycott as a rule, a government-mandated boycott, will be backed up by the forcible seizure of property or imprisonment by armed men prepared to do violence in the event of resistance or non–compliance.
Opt-in boycotts, boycotts not required by rules, can be non-violent as you rightly point out.
You can threaten non-violence, like a boycott.
Mr. Donovan is speaking of rules. A boycott as a rule, a government-mandated boycott, will be backed up by the forcible seizure of property or imprisonment by armed men prepared to do violence in the event of resistance or non–compliance.
Opt-in boycotts, boycotts not required by rules, can be non-violent as you rightly point out.