You didnt even watch the video do you? He's part of the syrian rebels.
Every westerners going there are not joining ISIS or Al-Qaeda.
There is 4 major sides in the Syrian civil war: government, rebel, ISIS, and kurds (and various minor factions). There is tension/friendship between those 4 groups, but certainly not everyone participating in this war is a terrorist or even a muslim.
Some people that went to Syria are actively helping defeat the governmental army of Syria, led by Bashar al-Assad. I hope that you want him to be dethroned as much as you want ISIS to be defeated.
He's Turk/Turkmen raised in Holland and like many of his kin he believes in Erdogan and is right wing nationalist (what Oberyn feels for France, this dude have same feelings for his homeland Turkey). It is very common for children of immigrants to turn this way, hell my young cousin who was born in Austria and is living in Vienna every day is posting Croatia stronk on Facebook and Instagram. He's obsessed with it. You Europeans believe you've give them all but they feel abandoned and thus form ghettos where they worship their fathers homeland.
It's a clash of cultures, their is warm and loving and you are a lot colder and depersonalized. Therefore they can't feel ya. I've personally had more success integrating with Northern American Asian mixed with Canadian community than I ever with this particular, largely European community. If you ask me, problem is within you and not rest of the world because only Europeans are emotionally reserved, people on other continents are much more open.
Now back to our dear Yilmaz. He's there to oppose Assad, because his hero Erdogan says Assad is the devil. What he's doing there beside participating in war himself. Teaching young people. Many of those are children born there and they will grow to become ISIL soldiers, simply because at this point they have no better option. He may not be ISIL soldier, but right now difference between rebels and ISIL is almost nonexistent and what Yilmaz is doing will strengthen ISIL forces.
He's probably dead by now.
