Labor leader Bill Shorten has urged the Jewish community to make its influential voice heard in the debate over watering down the current legal protections against racist hate speech – but he has also urged combatants to desist from inflammatory rhetoric.

In a speech to the Zionist Federation of Australia on Sunday before flying out to campaign in Western Australia’s senate by-election due April 5, the Labor leader reiterated his opposition to the Abbott government’s contentious overhaul of the Racial Discrimination Act, and told his audience there was now six weeks to persuade the Coalition to change course.

Shorten argued the government would be more inclined to listen to grass roots criticism than to criticism from the opposition. People have been invited to email submissions concerning the current RDA exposure draft to 18cconsulation@ag.gov.au by April 30.

The government’s reform proposal has triggered a fiery community debate between people who favour more unfettered free expression, and those who believe the RDA has helped set and safeguard a more tolerant tone of discussion on issues of race in Australia.

Human rights commissioner and free speech proponent Tim Wilson got himself in a tangle over the weekend over whether or he was defending the right of people to use racially loaded terms, including the word “nigger”.

Wilson took to Twitter on Sunday to clarify his comments. “Reports that I condone racist remarks are utterly false. I absolutely condemn racist language.”

The government’s overhaul has prompted public concern from some of its own backbenchers, notably Ken Wyatt and Zed Seselja; and some deeply personal interventions from Labor MPs outlining their own visceral experiences with racism.

Labor senator Nova Peris last week recounted an experience where she had been called a “nigger” on the sporting field. Labor’s senate leader Penny Wong also referenced some of her difficult experiences with racism.

The backlash has been fierce enough for the government to already telegraph it is open to changes. The prime minister signalled the package could be adjusted last Friday.

While urging activism against the government’s proposal, Shorten also issued a generalised warning against indulgence and over statement.

He said he didn’t accuse the prime minister, his attorney general, or the cabinet of being racists or bigots – or condoning racism or bigotry – with their current effort to rework sections of the RDA.

He professed not to be interested in Tony Abbott’s specific motivations on the RDA – whether or not the prime minister was acting in order to keep a promise to a “think-tank.”

Shorten said he was interested in the practical effect of the changes. The proposed rework was a “seriously retrograde step” – “a colossal mistake, and a dangerous one.”

The opposition leader validated arguments Jewish groups, including the Executive Council of Australian Jewry, have raised this past week against the proposed RDA changes.

“The Jewish people have been the target of bigoted abuse – of anti-Semitism – which is an old and wicked problem, and which is still with us today,” Shorten said Sunday.

“Section 18C empowers minorities with the ability to fight back, with the force of the law and the sanction of our state, in the face of the outrageous and malign, which could otherwise be the first step down a dark and evil path.”

But Shorten did not validate recent arguments from the foreign minister Julie Bishop, on the contentious subject of Israeli settlements. Since taking the foreign affairs portfolio last September, Bishop has shifted and “rebalanced” Australia’s foreign policy stance, and bucked conventional diplomatic wisdom, by arguing that Jewish settlements beyond the Green Line may not be illegal under international law.

Some Jewish groups are concerned that Labor has been drifting incrementally to a more pro-Palestine position, particularly under Bob Carr as foreign minister in the Gillard government.

Shorten offered this formulation to the Zionist Federation on the vexed issue of settlements on Sunday: “We do acknowledge that some settlement activity in the West Bank is illegal under Israeli law and we encourage the Israeli authorities to act effectively with respect to this.”

The Labor leader said a peace treaty between Israel and Palestine would ultimately resolve the argument once and for all. “The issue of Israeli settlements will be definitively concluded when there is a peace treaty, with defined borders – and then everyone knows the territory that Israel has, and that Palestine has.”

“So the real answer to the settlements is to reach a settlement. And the sooner that is done – the better,” he said.