Originally posted by Silent Master
The burden is on people claiming that the shield can stop a bomb/missile.
The burden of proof is not on them: it can block physical stuff...and that's is as far as they need to go. The only thing seen taking down a shield is magic: that is its limit (anti-shield magic).
The burden is now on the detractors to prove some sort of "near" physical limit exists.
A no-limits fallacy would be committed if they stated that it could withstand the forces of an 5-mile wide asteroid colliding with the shield and being unscathed. It is not known if the shields could withstand that or not. It very well could be that no amount of physical force can take out the shields and the only thing seen being able to take down a shield is anti-shield magic. It could be that a fired tank shell carries just enough kinetic force to break the shields (but this is false and you'll see why, later).
We can just as easily conclude that the shields can withstand any physical force as we can conclude that there is a limit. Both positions are almost equally illogical as neither was proven or disproved. Both positions are almost equally baseless (again, more on this, alter).
However, and this is the bane of the "no-limits fallacy" criers: Voldemort could have used a nuke on Hogwarts if a nuke would have actually worked: he had access to the muggle's technology and could have easily used it. He didn't so it would not have worked. Same with a tank shell.
Lastly, in cases of ambiguity regarding feats, it is up to the OP to specify whether or not something arbitrarily has a specific limit. You are not the OP so you cannot specify that it has a physical limit. Nor can anyone else except the OP.