The apology won't do him any good with the Arabs or the Stalinists in the Treason Party and the media, and I expect the President knows that. Where it will do him some good, though, is with the American public (outside of the wingnuts on the left and right fringes), who will now look at all further carping and crying by the fifth columnists as piling on, playing politics and generally failing to support the troops in contradiction to their pious bleatings to the contrary.
this is choir boy abuse in their world.
Another thing that will help the President overall. The jihadists can go back to cheerfully mangling the genitals of little girls with rusty tin can lids and buggering their little boys when the family goat's just not turning their crank any more and they get the urge to "jump some strange." It'll look just slightly hypocritical when our protests of these things draw nothing but raving demands that we "respect their culture."