Jay Sutherland, who later told reporters he intended to vote for the Labour Party, approached Ms Swinson during a campaign event in Glasgow.
Mr Sutherland said the effect of austerity in the city was "unforgivable".
He said: "People are dying here in poverty because of what you've done with austerity.
"I know people who have suffered so much, it breaks my heart.
Ms Swinson, who was flanked by Scottish Lib Dem leader Willie Rennie, replied: "I'd encourage you to look at what our plans are in this election."
Mr Sutherland branded the Lib Dem manifesto "not good enough".
He accused the party of "betraying students" in England, a reference to the decision not to push for scrapping of tuition fees, something which was a major point of the party's 2010 manifesto.
Mr Sutherland said: "I don't think they'll ever forgive you for that."
He claimed only the Labour Party would be able to stop Brexit, adding capitalism was "not a viable option to stop climate change", before describing himself as a socialist.
Mr Sutherland concluded: "Socialism is the only option to stop the climate disaster."
Ms Swinson, who served as an Under-Secretary for Employment Relations and Postal Affairs between 2012 and 2015, said the student was "entitled to that view", adding she believed capitalism is in need of reform.
Mr Sutherland ended the exchange by saying: "I think it's sad that you're here in Glasgow when this is the city that has been hit the hardest by austerity in Scotland."
Speaking after the exchange, Mr Rennie welcomed the challenge but said his party does not have a problem attracting young voters.
He told the PA news agency: "He seemed pretty knowledgeable and it's good that we have that conversation.
"I don't get that from most young people but it's good that Jay has strong views.
"You'll notice that we welcomed him in, we treated him with respect, we listened to what he had to say, he had a good minute or two with Jo.
"It's not like the other parties who would have bundled him away.
"We didn't feel threatened by him at all, because we're open to the discussion and the debate."
Mr Rennie said his party has "learned the lessons" of the coalition.
He added: "We understood what we got right and what we got wrong, some people will just focus on what we got wrong.
"There's a balance. These were difficult times and we did what we had to do.
"I think our manifesto recognises those challenges and wants to put those right."