I thought it was kind of an apples and oranges comparison. Yes, of course PCs try to exploit enemy weaknesses - Shadowrun is a tactical game. That doesn't justify the GM excessively exploiting PC weaknesses. That's comparing in-game behavior to metagame behavior. The NPCs are the ones who should be exploiting PC weaknesses, and they should be limited to their own knowledge, not the GM's omnicient view. In other words, the enemy wage mage might look at two characters and cast his stunbolt at the troll with a Willpower of 5, instead of the hacker with a Willpower of 2, because he'll think "Hey, big dumb trog." Obviously, if the group makes a recurring enemy who knows about some of the group's weaknesses, or if a PC's weakness is well known or blatatly obvious, it's a different story.