If you don't trust someone's judgement, why would you apply to join a campaign managed by that someone?
As long as you trust the campaign manager, I don't really see a reason not to join.
I'd say anyone who thinks that way ("will this affect my signature earnings if I make this exclusion") shouldn't be allowed anywhere near the trust system
If someone excludes a campaign manager from his Trust lists and applies for a campaign, doesn't that show he doesn't care about potential financial consequences? Even better if the campaign manager still accepts him (assuming he qualifies), to show his skin is thick enough to separate the exclusion from business.