I agree with most of what you say. The only thing missing is the reliance on past precedent. Corporate sponsorship has been done dozens of times before with the likes of Sara Lee, Nestle, Carnation, Coke, Edy's just to name a few, and in none of those instances did anyone declare that the sky was falling and that a particular location had been ruined. And while: "Disney will do this the right way and keep the location pleasant" is indeed an opinion, it is one formed from vast past experience whereas: "Disney is going to ruin this location" is an opinion formed by little more than fear. People are entitled to either opinion. But one comes with precedent and the other does not.
One opinion formed by fear of losing something, another by promise to get something. Both opinions based on personal feelings and nothing else. While Disney usually does a great job in anything, they also do mistakes, so expecting either is perfectly acceptable. As for other sponsors, if they just announced that they now sell SB it would feel different. How place will turn to be, nobody knows but there is a lot of room for speculation either way.