'Making a Murderer' Bomb Threat Caller ... I Want 'Justice' for Steven Avery!

Someone got real pissed off watching "Making a Murderer" ... a bomb threat was called in to Manitowoc cops and the caller demanded justice for Steven Avery.

The caller claimed there were bombs planted all over the Manitowoc County Sheriff's Department and in its parking lot on Wednesday evening. Deputies cleared the building and searched for a couple of hours before giving the all clear.

No explosives were found.

Cops say the caller mentioned "getting justice for Steven."

The 10-part documentary about Avery's 2007 murder conviction has angered many viewers, though none to the point of phoning in bomb threats ... before Wednesday night.