No, it shouldn't. If the banking system engages in risky behavior, such as willfully doing billions of dollars in business with people who inflate the value of their property, that's a problem. As I said in another thread, if it's one client, that's one thing, but I seriously doubt Donald Trump is the only one getting that kind of treatment.
With that being said, that raises the obvious question: why not do more to regulate and punish the banks in that situation? That would be a fair question to raise. And yes, I'll say it up front: they wouldn't have ever gone after Trump had he not become a political figure. But that can be said of many political figures who've been prosecuted in the past (see Bill Clinton).