PORTLAND — Former U.S. Rep. Barney Frank told an audience of nearly 500 people in Portland on Monday that refusing to vote insults the memory of Dr. Martin Luther King Jr.

The Portland branch of the NAACP held its 34th annual Martin Luther King Jr. Day breakfast at the Holiday Inn By the Bay and gave special focus to the 50th anniversary of the Voting Rights Act of 1965. King advocated vociferously for increased protections for voters while many blacks around the country were being attacked and intimidated to prevent them from going to the polls.

Frank, a liberal Democrat from Massachusetts who was the first member of Congress to come out as openly gay in 1987, was the keynote speaker for the Portland event.

“[King] was ready to die to give people the right to vote,” Frank said. “How dare people give that up because of some ideological complaint.”

The former congressman blasted what he called “a double-barrelled assault on voting in America” by conservatives, whom he blamed for a U.S. Supreme Court decision in 2013 to weaken the Voting Rights Act, as well as more local voter regulation efforts pursued under the auspice of what he called the “non-existent problem of voter fraud.”

In Maine, several Republicans in recent years have sought to reduce the window of time for submitting absentee ballots and tighten voter identification mandates, efforts supporters said would curb voter fraud but opponents — mostly Democrats — argued would just make it harder for people to vote legally.

Frank saved perhaps his most biting criticisms for liberal activists who have taken to the streets in protest in recent years but who have stopped short of political engagement. He said King plotted his demonstrations very carefully, with specific goals in mind.

“Acting out because it makes you feel better … is an indulgence reasonable people can’t afford,” Frank said. “An idealism that pays no attention to whether or not anything gets accomplished just makes you feel good.”

While he didn’t mention any particular group by name, many members of the Occupy movement — which spread across the U.S. with public protests and encampments in 2011 — argued for some social and financial reforms included on left-wing political platforms but abstained from voting or other political activities because of the argument that corporate money drowns out all other influence anyway. That sentiment has echoed through occasional anti-government protests in Portland and elsewhere since the Occupy camps disbanded in 2012.

“We can’t undo that Supreme Court decision unless we win some more elections, and we can’t win some more elections if people are sitting at home saying, ‘Why even bother?’” Frank said.

The former congressman married Mainer James Ready in 2012 and has been a political ally of Maine’s 1st District U.S. Rep. Chellie Pingree, a fellow Democrat who introduced him at the NAACP event Monday morning.

Pingree said Frank was among the freedom rights advocates who traveled by bus to Mississippi five decades ago to organize voter registration drives and convince blacks in the racially divided state to go to the polls.

“Fifty years isn’t that long ago in our country,” Pingree told the Portland crowd. “We still have so much work to do.”

Others to address the audience Monday in Portland included city Mayor Michael Brennan, state Sen. Justin Alfond, D-Portland, NAACP Portland branch president Rachel Talbot Ross and local high school students participating in the King Fellows youth group.