Actually Black/White/Black2/White2 are DSi enhanced titles and are compatible with WPA and WPA2 provided you play them on a DSi, DSi XL, 3DS or 3DS XL.
My home Wi-Fi is encrypted with WPA2 and I have no issues connecting to Nintendo WFC to trade, battle, download events or use the GTS in Black and White.
The problem that the TC has lies with the fact that he's using an older model DS. Anything DSi or newer is capable of using WPA2. I have the basic DSi and the basic 3DS, both of which work perfectly fine with WPA2.