Here's a quick suggestion on how to avoid this situation:
Don't neg a mod. If you feel the need to neg someone it should be a new person who has just gotten 75 rep to view the vids, has seen the vids, and then with your neg they can't see the vids. This will then prompt said person to go on a tirade about how they can't view the vids anymore which will in turn get more negative reps
In all seriousness if you feel the need to neg someone who has infinity rep, mod or not, you better not just say something stupid like "your sig is gay". If you really don't like the sig and feel it deserves a neg rep then you should at least put something funny in it. Like if you really wanted to comment on how homosexual his sig is you should have said something like "hey your sig is a whore. it got my friend drunk and made him gay. That's not cool so I neg you for it". Whenever I neg someone it is always for breaking a rule or skirting it or just trying to derail a thread. And I always explain why rather than say "fuck off" or whatever else people have put in their negs against me.
Oh and this thread is epic - like these: