This is nothing new, these stamps have been out since 2001.
There are U.S. Postal Service (USPS) stamps commemorating the EID season during the Muslim period of fasting and prayer known as Ramadan.
According to the United States Post Office website the stamp has had several issues in various denominations spanning from 34 cents in 2001 to 41 cents in 2007. The latest release was announced August 12, 2011 with a "Forever" denomination, which means that its value will remain constant with any increases in first class postage.
Obama had nothing to do with this stamp, which was first announced during President George W. Bush’s administration, on Aug. 1, 2001, honoring two Muslim holidays, including Eid al-Fitr, the first day following the month of Ramadan, a period of fasting and religious observances. The stamp first came out at 34 cents, the prevailing first class rate at the time. It has been reissued several times whenever that rate increased.
I see nothing wrong here. Being Muslim is no different than being Christian. It is how one conducts themselves which shows where their faith lay.