If someone giving negative feedbacks for no reason or with reason it won't reflect in your default trust rating unless they are DT members so you can continue to do the good job of finding the scammers irrespective of which rank you are.
Bitcointalk have no such rules to punish such profiles and they take advantage of this.
Actually we have,
Trust spam isn't allowed. If I see anyone posting dozens of fake trust ratings (from one account or many alt accounts),I will delete all of their ratings.