Bricking the cart is technically just as bad as bricking the console. I could live with SD cart corruption though.
Yes, but 4.5 3DSes are discontinued while 3DS flashcards aren't.
Right now, only 4.5 3DSes can use the DS profile exploit to run Gateway. Every 4.5 3DS bricked is a 4.5 3DS lost that cannot re-appear (apart from using the recent un-bricking program for the Raspberry Pi and such, but that's very complicated for now.)
If they just bricked the clone flashcards (with them making 100% sure it wouldn't brick Gateways), then the user could just go and buy a legit Gateway instead, but since they brick the 3DS itself, the clone user can't even go and convert to a Gateway user, which is counter-productive for the GW team.
From a legal point of view, sure, they'd be destroying private property in both cases (and nobody would like having something they spent ~50-60 bucks on destroyed), but I would say that destroying clone cards instead of 4.5 3DSes would be the lesser of the two evils.
Of course, they *could* also decide not to brick anything at all, but yeah, I don't think the Gateway team would be willing to do that.