The appearance of impropriety

Clarence Thomas was treated to gifts and favors from a variety of wealthy conservatives which he didn't disclose.  His house, in which his mother lived, was bought and his mother allowed to continue to live there rent free. He enjoyed vacations and flights on private planes.  Although it all looks very fishy it's not corruption, at least as the law understands it. There is no evidence of a direct "quid-pro-quo".

However the strict legal definition of corruption is really not that important here. What does matter is impropriety and the appearance of impropriety as the Founding Fathers noted. 

It's hard to say if Thomas' rulings were directly influenced by his wealthy friends lavishing him with gifts or whether their friendship arose and was sustained by a shared world view. 

Nevertheless, that fact they became friends only after he was appointed to the Supreme Court, while not in and of itself improper, it could be construed as a conscious attempt by his benefactors to exert some subtle influence in his general thinking even if not directly on his legal opinions.

The second question which Journalists haven't looked at (and which I think they should) is whether his donors sought out and then lavished similar gifts on other like-minded thinkers or whether their "outreach" was only to those who wielded significant power.  If that were to be the case it would look suspiciously like an attempt to influence Thomas' (and other powerful peoples') decision-making and hence his opinions.

Since the Court like many important institutions of democracy relies on public trust (just as banks do, as First Republic has just shown us), the appearance of impropriety undermines that trust and so creates instability in society. 

SCOTUS needs to get its ethical act together for the good of the country and do so without Congress getting involved. Showing it can police itself will be important to restoring trust; having ethical rules imposed on it from outside will only reinforce that idea as an institution it cannot be trusted to do the right thing.