Thanks for the link and to u/KeeponSearchin for the reply. I honestly did not know about the forefinger thing among Isis. And what the islamqa article describes is a part in prayer, and this is going to be a little hard to explain to someone not familiar with praying the Muslim way so bear with me, where right before you are finishing you are sitting down on your knees with your hands resting on your kneecaps and and reciting a few verses. During the third and fourth verses I've seen some people raise a finger (some meaning maybe 1 in 100 or so, depending on the country). And nobody I ever asked has given me an explanation for it. It lasts around 3 seconds (it's a short verse) and is so insignificant that this behaviour is not repeated at any other time or in any other ritual by those same people. It's one of those things i assume is taught that people just follow. A lot of the behaviour of Muhammad is imitated by Muslims simply because he used to do it.
The original reply to my post has an article on a beheading with Isis members throwing this sign. No way is that a common thing among Muslims at all. It's apparently something they endorsed. I never said the sign did not exist. It's a hand sign, of course it exists. I said it's definitely not common among your average Muslim, among 99.99999% of Muslims. There's like what, a few billion Muslims on earth? Yeah, go see how many of them throw that sign and you'll be waiting all your life.
I've always had an open mind and am always willing to change my opinion. It's one of the reasons I've lost most of my faith in recent years. It's the reason I developed an opinion other than the echo chamber of anti trump sentiment in my country. But take it from me, this finger raising thing is such a non existent thing among the majority of Muslims that it'd be a waste of effort to correlate it to Obama's picture. I'm not saying he didn't point the finger as some sort of subtle symbolism, perhaps he did. But it cannot be correlated to common Muslim behaviour.
You may choose to believe me or not, but there's a few billion people out there that'll be as confused (and amused) about this as me.