I don't get the "ISIS hasn't killed anyone yet" argument. As the threat grows and they are actively looking to attack us, it seems silly to say "they didn't before so why would they start now?". I mean the Nazis didn't attack us on our soil, but we knew they threatened our way of life. And more importantly the lives or our allies.
Yea, but to be fair we were perfectly content letting them continue on their merry way until their ally did actually attack us.
So you would suggest we wait until a large number of Americans lose their lives before we get involved in this conflict?
I was really just saying it was a crappy analogy.

The actual issue is obviously a tough one. How do you even know that you successfully prevented an attack on U.S. soil by going after terrorists in the Middle East? Sure, you could end up with zero attacks in the U.S., but it's possible you would also have that number if you weren't proactive.
The only thing I know for sure is that terrorism is a tricky beast. ISIS has hideouts, but it is not a nation. It's an ideology with followers. Our best weapon against a radical ideology is culture, not guns. You can't ever stop really bad people from trying to use their religion to manipulate the masses to follow them, but you can try appealing to the masses by convincing them America doesn't want to oppress them and own the Middle East.
I'm sure a lot of the current ISIS recruits only know America by our destruction of their homes in the name of fighting terrorism.