If you distrust a campaign manager, why would you join a campaign he manages?
If you distrust him, it is because you think he will scam you or someone else.
Joining a campaign of someone you distrust makes no sense
Now, what's the correlation between distrust and scam? read.
You should add users who left accurate feedback and have good Trust lists to your Trust list, and you should exclude users who leave inaccurate feedback.
This means your Trust list should be based on how you value the users' judgement on others, and it should not be based on whether or not you Trust those users (with money) or traded with them.
Imagine a campaign manager run the campaign smoothly without any scam, but this user leave inaccurate feedback.
This mean the manager isn't scammer, but he deserved to be included in distrust list. What's wrong to participate in his campaign when he's not a scammer?