There is no actual way of "destroying coins". Even sending to an address with a private key that isn't known, a person can also get a lot (and i mean a real lot) amount of hashpower to bruteforce the key. Although it would be difficult, the coins are still recoverable.
Coins can be mined out of existence (miner selects a reward less than the max allowed).
Still coins sent to addresses with no known private key are effectively lost. No you can't brute force it with a lot of hashing power (not even all the computing power on the planet). If you could then Bitcoin would be worthless.
As far as I know, you can perfectly try and bruteforce a bitcoin address. By simply using VanityGen. Your odds will be next to zero, but that DOES NOT mean it is impossible. Also, how do you know that in the near future there won't be asics capable of doing so?
D&T knows that ASICs won't be capable of doing so because, like everyone else who assures you of that, he has done the maths. There's nothing more to add to that (by now cliched, but for good reason) sun pic. When a non-zero probability becomes sufficiently small, it becomes foolish and obscurantist to continue to treat it as "0.0000001". What part of "made of something other than matter or occupying something other than space" is relevant to ASIC design? The argument presented in that sun pic is dependent ONLY upon very well tested deep laws of physics. Nobody is going to design an ASIC that breaks the laws of thermodynamics until some time well AFTER a theoretical physicist has shown those laws don't hold, which is a remote and non-quantifiable possibility.