McCain has a habit of saying this and related bits of "Iraq Forever" cheerleading and then claiming he was misinterpreted, so I'd like to address this point to him directly:
I understand that what you are REALLY saying is that you want our troops to stay in Iraq forever without dying but with magical flowers and happiness. When Democrats criticise you for saying this, they really are critisizing this position, not just misunderstanding it. The reason we criticise it is:
1) Saying that you want our troops to not die is not the same thing as having an actual plan to ensure that they do not die. My plan is to eat huge quantities of food, but to do it without getting fat. The fact that I have no actual mechanism to make this happen means it is a stupid thing to say in the first place.
2) Even if our troops were, in fact, not dying it would still be a bad idea to permanently occupy a Middle Eastern nation in which our presence is itself a source of instability - if for no other reason than that it lures to our enemies in the region into once again making our troops die (see point one).
I can explain it to you in simpler words if you like. Try this: What you are saying is BOTH a stupid thing to say AND a bad policy. That is why we mock you for it.