I don't understand. You seem to be emphsazing the point that there's no real difference in principle. The question is this: why would it be okay to purchase a new account in order to subvert the trust system but it's not okay to simple purchase trust to subvert the trust system. They are both ways to subvert the trust system but one is okay whereas the other isn't.
There isn't much to understand. Why is selling trusted accounts ok? Because people say so. Why is selling trust not ok? Because people say so. There aren't rules, the community as a whole dictates what is ok and what isn't ok to do. For example, leaving feedback for someone you haven't traded with. Why is that ok? People have rationalized that it is necessary to preempt scammers, so it is an accepted practice, not a rule.
If I had to take a stab at guessing why people care more strongly about trust selling, is because the initial trust they receive could be a lie. Lets say someone has an account that they have completed 10 successful trades and have 10 positive feedback that they are selling. The trust adds to the value of the account. That value then is carried along at the time of sale. So say an account is 1 BTC, and the trusted account is worth 1.5 BTC because of the trust, the sale price is going to be 1.5 BTC, meaning the scammer buying the account will need to scam more than the 1.5 BTC, otherwise they lost money. Generally an account is going to be worth more than its trust because of the time put into the account, and sig campaigns, etc. I believe that is why buying trusted accounts to scam isn't a commonplace thing. Its just not profitable, but I could be entirely wrong, that is just my theory.
Say you wanted to buy trust, not the account. Your account is worth 1 BTC. You pay 0.1 BTC for the trust, and the feedback says that you were trusted with 50 BTC. Your account might then be worth 2 BTC (That is if people don't just disregard that kind of feedback from non well known people) you can then try to scam for 2 BTC, and if you succeed you made .9 BTC, making the act of buying trust possibly feasible.
That said, I still don't think that either is a commonplace thing, because all it takes is one guy to say, hey that trade looks fishy, make a thread about it, and everyone involved is marked a scammer, and whoever trusted that person on default trust on the first place would have to deal with a lot.... and I mean a lot of hate.
That all said, there were a lot of rational details that people overlooked here, so their panties got into a wad for nothing. First the OP didn't have a default trust account, they had no understanding of how the trust system worked. If they did have a trusted account, it was most likely on trust depth 3/4 which would be relatively meaningless. We don't know how much the OP was charging for trust and we don't know if their trusted account had any weight at all. I actually hoped that they did have a trusted account, because the only way to see how it would have all played out. I have a few theories on why selling trust isn't profitable either, but we would have had to see it in action.
So in conclusion, what is ok and not ok is dictated by the community. I think that people are more outraged by trust selling because it is more likely to be profitable for a scammer than buying an account outright. The reason the trust system has been in place this long and this topic is just coming up sort of speaks for itself.