He is an asshole because instead of simply saying that the problem is difficult (which I already know) or suggesting a possible solution, he preferred to say that it is impossible and to offend me for having the audacity to want to find a solution where he failed.
As for your answer, I will introduce what I am thinking using your own example: I want to prevent the elephant from being devoured by the ants, what can I do? The most obvious is to take the elephant off the place, works 100%. But I need the elephant in the place so I can not get him out of the place, but I still can not let the ants eat him. I can then eliminate the ants by using a flamethrower, which also works but I have no way of knowing how many ants I'm dealing with. I can then prevent the ants from reaching the elephant by placing the elephant inside a crated box, but I need termites (valid traffic) to reach the elephant, so I have to differentiate the termites from the ants. Do you see where this is going? Options to try to solve the problem exist, the problem is to find which option works in a situation where it will not have obvious solutions.