Barack Obama may have done too little when he was president to counter Russia’s subversion of our democracy on social media. Now, however, he’s trying to make up for lost time.

The former president spoke at Stanford University on April 21 to lay out his vision for fighting disinformation on the Internet. His focus on the subject is fitting; the dusk of his administration marked a turning point from techno-optimism to pessimism after election interference revealed how easily malicious actors could exploit the free flow of information. But whatever blame the White House deserved in 2016 for failing to speak publicly about or retaliate against Moscow’s incursions, Congress and companies have fallen even shorter in the years since by failing to enact reforms — or reform themselves.

That’s where Mr. Obama’s ideas come in. His diagnosis is on target. The Internet has given us access to more people, more opportunities and more knowledge. This has helped activists drum up attention for overlooked causes. It has also enabled the nation’s adversaries to play on our preexisting prejudices and divisions to sow discord.