The US President used his address to the G20 summit to issue a humanitarian rallying call to world leaders in the face of the terrorist threat.
He urged them not to turn their back on those fleeing civil war and strife, praising German Chancellor Angela Merkel for her courageous stance in offering help.
He also praised conference host Turkey, which has accepted more than two and a half million refugees.
Then he turned his focus to his critics back in the United States.
"And when I hear folks say, 'Well maybe we should just admit the Christians and not the Muslims', when I hear political leaders suggesting there would be a religious test, when some of those folks themselves came from families who benefited from protection when they were fleeing political persecution, that's shameful. That's not American. That's not who we are. We don't have religious tests to our compassion."
It was a view echoed by Turkish President Recep Tayyip Erdogan.
"Terrorism does not know any religion, nation, race, region. It is extremely wrong to associate terrorism with any specific religion and in fact doing so is a big insult."
Much of the conference focus was on Syria with President Obama hailing the fact world leaders had, for the first time, agreed on a two-year, Syrian-led and Syrian-owned political transition in the war-torn country.
But he acknowledged there were still many hurdles ahead in the quest for peace.
"Hopes for diplomacy in Syria have been dashed before and there are still a number of ways that this diplomatic push could falter and there are still disagreements between the parties, particularly over the fate of Bashar Al Assad, who we don't believe has a role in Syria's future because his brutal rule, his war against the Syrian people, is the primary root cause of this crisis."
Russian counterpart Vladimir Putin was sounding a conciliatory note, saying after the Paris attacks, it's time for greater cooperation between countries.
"We have never refused to have good relations with our partners either in the east or in the west and these unilateral steps restricting that cooperation were initiated not by us but by our partners. If now our partners say that the time has come to somehow change our relationship we would welcome it. We have never rejected joint work and never closed doors."
Not so sanguine is British Prime Minister David Cameron, who warns any attempt to impose a political deal on Syria from outside won't work - any new deal must be accepted by the people.
"You need to find people in the Government who can back Christians, Sunnis, Kurds, Alawites so that government represents all of Syria. And that's the process that needs to be gone through."
While Russia is now prepared to support Syria's opposition with air strikes in its fight against IS, newly-elected Canadian Prime Minister, Justin Trudeau, is sticking to his pledge to scale back Canada's role.
"We made a clear commitment in the campaign to stop the bombing mission by Canadian jets and to replace it with a role for Canada that was still a serious military role but leaned more towards training of local troops to be able to bring the fight directly to ISIL. That's the commitment we made very clearly throughout the campaign and we have a mandate to do that."
Prime Minister Malcolm Turnbull left the conference heartened by progress on Syria.
"The outcome that we want is a resolution, a stabilisation in Syria and a transition to a government that has broad support and a restoration of peace so that order can be restored and of course those millions of refugees can go back to the homes that they want to return to."
