General threats of violence are far less actionable that specific threats to a specific person, which should be reported to law enforcement.
The much larger issue, and you can't pretend to be oblivious to this, is the public policy position announced by your leaders. Many people who do not value a civil discussion of policy choices find logic in a violent end to NRA members for the sole reason that it appears the NRA thinks a violent end is OK for others.
What can be done? Maybe a mass resignation of NRA members will cause your leaders to rethink the disastrous policies they announced this weekend.
This answer is offered as a public service for general information only and may not be relied upon as legal advice.
Contact the police if there is a reasonable threat.
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