Unfortunately, the definition of sexism has become so broad that almost anything could qualify. Consequently, it's all too easy to find yourself in a damned-if-you-do, damned-if-you-don't situation.

In the case Plants vs. Zombies, the plants are essentially asexual, which means any female characters would have to be zombies. Zombies only do two things in that game: eat and die.

Even if there HAD been female zombies, I'm sure someone would STILL complain that it's sexist. Why? Because the game encourages players to act out violent fantasies against ugly women who eat too much.