I hate to sound like a Blizzard fanboy by saying this, but I'm wondering if the people specifically using trainers and cheats were using them just to get achievements. While it doesn't make it any better, the Battle.net system is an online system and in a sense, they are still exploiting the online mechanics of the game. There are rewards for getting certain achievements as well, so if people are exploiting the game just to get those rewards then I kind of understand Blizzard's stance on it.
I know with WoW's achievement system people have exploited certain mechanics of the game and have gotten banned or suspended for it, just because they were trying to up their achievement score.
The key thing here is that with Starcraft and I'm guessing with all new Blizzard games in general, you're still online while playing single player. I guess if you really want to cheat or use trainers, you should probably play in offline mode altogether (which would disable achievements).