At the time of this Lego Fun Facts PDF from 2009, there were at least 4 billion minifigs that had been produced.
They sell 3.9 minifigs/second which is 122,990,400 per year. (3.9/second * 60 seconds* 60 mintues * 24 hours * 365 days in a year)
So there were 4 billion in 2009 + 1,229,904,000 (10 years * 122,990,400 figs/year) = 5,229,904,000.
According to a UN prediction, the world population in 2019 would be 7,641,372,898,000 which is considerably higher than the 5,229,904,000 figure for Lego minifigs.
The authors of the PDF were Julie Stern and Karen Lynch.
Julie Stern's Linked In profile shows her as being a Brand Relations Manager for Lego from 2002-2011.
Karen Lynch, now known as Karen Nolan, works for Flashpoint PR which is a PR firm that Lego uses.
So the answer to your question would be that the claim is incorrect. But keep in mind that my figures were calculated using the rate as which Lego sold minifigs in 2009, not produced, as this was the only figure I could find.
Additional calculations to see when the minifigs might overtake the human population.
2029 World - 8,464,764,831,000 Minifig - 6,459,808,000
2039 World - 9,254,752,148,000 MiniFig - 7,689,712,000
2049 World - 10,117,522,812,000 MiniFig - 8,919,616,000
2059 World - 11,132,821,140,000 MiniFig - 10,149,520,000
2069 World - 12,434,173,955,000 MiniFig - 11,379,424,000
2079 World - 14,169,449,904,000 MiniFig - 12,609,328,000
Since I am not able to make assumptions about how the minifig production rate may/may not increase I decided to stop as this point as the rate of the population growth per decade was higher than the calculated minifigs/decade rate.