1) They are holding a large short position and getting people to sell in mass, pushes the price down further (benefiting a short position)
2) Ultimately they really felt oil might go up in the near term, so making statements that gets the public to sell in mass, could then provide Goldman Sachs with a potentially attractive buy price for oil and oil related companies.
3) They really are bearish on oil now, but that doesn't explain why they didn't tell their clients only (if their clients are selling along with the public, the price goes down even faster, and the selling execution price may not be attractive.
Bank of America Bullish on Oil ConocoPhillips 5 day Stock Chart
Yahoo Article on Oil Prices
Following Goldman Sachs' negative call on crude prices which took the wind out of the commodities rally this week, Bank of America Merrill Lynch is predicting a 30 percent chance that Brent crude could hit 160 dollars a barrel in 2011.
"Commodity prices should move broadly higher in 2011 on robust economic growth in emerging markets, despite relatively weaker growth in developed markets," said Sabine Schels, a commodity strategist at BoA Merrill Lynch in London in a research note.
"With oil demand expanding rapidly and Libya production down by at least 1 million barrels per day, we forecast (the) Brent crude oil price to average 122 dollars a barrel in the second quarter, and believe prices could briefly break through 140 dollars in the next 3 months," she said.
Given the risks from the situation in the Middle-East and North Africa, Schels says there is a chance the price could go even higher over the next 2 months.
"Under our upside risk scenario, Brent prices could average this year between 125 dollars a barrel and 160 dollars a barrel," Schels said