'placate anger' is correct and can be used in written English.
You can use it to describe a situation in which someone does something to reduce or alleviate someone else's anger. For example, "He tried to placate his mother's anger by apologizing and offering to buy her flowers."
However, the operation has appeared less successful in placating anger on Okinawa, a southern island far from the tsunami area that feels it bears an unfair burden in hosting about half of the 50,000 United States military personnel stationed in Japan.
Holder's announcement was not enough to placate the anger in the city.
On March 5th China's president, Xi Jinping, vowed to act "without mercy" against corruption in an effort to placate public anger.
To placate that anger, he vowed that, once in power, he would rein in the excesses of this law that he oh-so-reluctantly supported.
To placate unionist anger, Sinn Fein offered to re-route their parade away from the town's war memorial and a local Methodist church out of which many of the IRA's local victims were buried during the Troubles.
The Epistle to the Hebrews also posits a novel interpretation of the Crucifixion, Wills argues, that of substitutionary atonement: the death of Jesus was necessary to placate the anger of a wrathful God against a sinful humanity.
Fourteen Alsatians convicted of taking part in a massacre at Oradour in 1944, the war's worst atrocity on French soil, were given amnesty by the state to placate Alsatian anger.
To placate growing anger over having been kept in the dark and misled, the spying agency gave a private briefing to rank-and-file members of Congress about programs of which they had previously been unaware.
The New York Times' Simon Romero has a good article from yesterday on the thus-far-unsuccessful attempts by Obama to placate the anger in the region from this report.
Last week, the government and the Scottish authorities released, separately, thick files of correspondence between them on the issue, each effectively seeking to placate the anger of the Obama administration and American families of bombing victims.
