Can someone please explain to me why it says to fight against those who don't believe? don't you think thats a bit extreme? and maybe thats why there is so much violence from those muslim extremists?

29. Fight those who believe not in Allah nor the Last Day, nor hold that forbidden which hath been forbidden by Allah and His Messenger, nor acknowledge the religion of Truth, (even if they are) of the People of the Book, until they pay the Jizya with willing submission, and feel themselves subdued.