I think, if you have a saboteur, they're probably not part of your 'network'. The people you've endorsed probably won't have endorsed the saboteur, so the saboteurs activity should not effect your feed in any meaningful way. This is how trust works in real social circles.

Moderators clearly work but it's a shame it relies on single people doing a good thing. It's a shame the moderation can't be done by everyone all the time, unconsciously.