After the arrest of Harvard scholar Prof. Henry Louis Gates and the subsequent dropping of charges, Obama further fueled the controversy by taking sides with the black scholar who happened to be his old friend. The result wasn't as Obama had expected. Sergeant Crowley from the Cambridge Police department was quick to defend his men and said that his men were following the procedures and the President reacted in haste.
This incident further fueled the controversy and it hasn't been going too favorably for Obama so far. The President did realize that he should have checked more details about the incident before reacting and said that he had the greatest respect for policemen of his country.
But this isn't enough as it would seem since Obama has now invited both Sgt. Crowley and Prof. Gates for a beer at the White House. This is another attempt by him to subdue the situation aggravated by him and being a beer buff himself, he thought what's a better way to do it than over a beer.