SAM,
If its existence or nonexistence of God we are debating, then I fail to see how it is not an opinion. You either believe there is a bus or you don't. Thats an opinion. Are you going to stand at the bus stop or will you walk away?
So here is an easy question for you in the black or white style you are suggesting.
Do I own a dog?
What you are suggesting is that you can only answer with -
1. I believe you own a dog.
2. I believe you do not own a dog.
Does it really make any sense to assert a belief of any type when you do not have adequate information?
Which means we must have -
3. I have no belief whether you have a dog or not.
Now the question, do gods exist -
1. I believe gods exist.
2. I believe gods do not exist.
In the same way as above, we must also accept that the next option be available -
3. I have no belief that gods do or do not exist.
Conclusion.
When there is inadequate information or inadequate evidence for a proposition then it makes no sense to assert a belief, for either case.
There are always 3 options in these scenarios and not the 2 that you are trying to insist.