Countering Master Enslave...

[Atreidi]

I love using master Enslave on enemies then using their weak units on suisidal attacks. Its all fun and games.
I've never seen the computer use it, but I am sure human players do. When they do how do you counter it?

This spell is too easy to cast. On a Big map, late game it is quite easy to havle high level astral mages that can cast the spell. How do you avoid someone casting Master Enslave then retreating? Or how do you avoid getting all your units converted? What to do other than "pray for the random" factor to kick in and not convert them?