Actually, no fig a would not be able to destroy that section of wall for this reason that hasn't been brought up yet. The LOF from the attacker must pass through the section of the wall being destroyed. if it passes through another section then it is blocked and would have to be destroyed first.
Fig B would never have a LOF to destroy that section of wall even if there were no other wall section blocking his lof.
Fic C could not destroy that section of wall from it's current postion. While it can draw a LOF to both squares on either side of the wall, neither if them go through the wall.
Fig A is the only one who can destroy that wall from his current position using the green line.

But as was stated, A only has a range of 6, so at the moment, even A could not destroy the wall section. Now if A had his range increased by 1, then he could destroy that wall section.

XO-Man-O-War, does it state what you just said about the LOS needing to pass through the section of wall being destroyed somewhere in the rules or a FAQ somewhere? We have this terribly annally retentive player at our venu....actually it was he whom I was playing when this whole situation came up. I need clear definative proof when dealing with him. You and I are both in agreement that what you say is how it is "meant to be"....but he's going to argue the letter of the rule. If it just sez "must have LOS to both squares" then he's going to enturpret that C could destroy that section of wall.

You know I looked for it and couldn't find where it spells it out but if you think about it for a sec you don't need it spelled out.

If you are shooting at a fig and the LOF crosses a wall section (blocking terrain) it is blocked. It is no different when you are trying to target another section of wall. IF your LOF crosses another section of wall that you are not targeting, then the LOF is blocked.

I forgot about the range thing. I was gong to say something about you having to have range to the square on the other side of the section of wall you are wanting to destroy but I forgot. Oops.

Before Icons, couldn't figure C target and destroy that wall?

AFAIK, it was just a 'forum ruling' on the judges forum. I DO remember a very lengthy discussion about this whole thing, and this was the outcome. I'll see if I can find it and post it here.

Remember though, if you are the judge, your rulings are the law. You can listen to what he says, but if you rule differently, he must abide by your decision. And if it turns out your decision was wrong, you correct it the next time you get together and move on.