The question is, why this user have to be subscribed to DefaultTrust?
Because the rate of new users getting scammed would be ridiculous otherwise.Why a new user should trust unknown users from the first second of being on the forum? And what about one of the main principle? -- Dont trust. Verify.
That is nonsense that can't be applied to this. Who are you going to trade with, some random that never did paypal-to-btc or someone who has 100+ such succesful changes? Oh right, don't trust verify the 0-trade-newbie offering reversible methods of payment. 
<- shows how absurd your attempt is.