First off, protection implies PREVENTING something, not acting on it. That said, I'm wondering why you didn't read the helpfile when encountering this problem. Had you done so, you would have noticed two things:
1. in any event, $nick is ALWAYS the user triggering the event. now the one triggering the on DEOP event, is the one on the active side of it, not the receiving side.
2. according to the helpfile, (and I quote) "$opnick refers to the nickname of the person being opped/deopped".
3. did you ever consider the possibility whoever is deopping you might have a very valid reason for doing so? gonna get real popular this way