It really isn't. In your example, it would not be silly for me to conclude I should go to the restaurant to buy lunch. It would be silly to conclude that, unequivocally, I have to be able to get lunch at the restaurant.

To use your analogy, you have two sides arguing about the restaurant:

1) Side A is suggesting that the restaurant absolutely has to sell me lunch.
2) Side B is suggesting that the restaurant absolutely will not sell me lunch.

I'm on Side C, the side arguing to drive there and see if they sell you lunch, but don't cry if they don't. I'm not arguing against the presumption, I'm arguing against the zealotry. The argument itself is the stupid part, there's no need to argue. This is our current understanding - it may or may not be complete, is a perfectly fair and reasonable assertion. If you see the reactions of "Pro Science" vs "Pro Religion", both sides are equally absurd.

Bear in mind the back and forth between me and team evolution started with the assertion that "We probably don't know everything about it" and people arguing with me otherwise.

Edit:

In essence, you and I are saying the same thing. I would argue that team evolution is not saying "this is our current understanding", they're saying "this is the way things are". While the two statements sound alike, they're not quite the same thing. Any time you utter the latter phrase, you're probably wrong. Science itself may never assume its wholely and unequivocally correct about everything, people however do make those assumptions. Based on the way Nightgaunt phrased the question, I'm assuming he was interested in knowing what people think absolutely, in mock of religion.