He definitely should have disclosed the gifts. I'm don't agree with mandating who people are friends with. I would love to have rich friends as well. It also is not surprising that a conservative judge would have conservative friends. But he should have disclosed the gifts.
Accepting millions of dollars worth of gifts influences people. PERIOD. Having friends doesn't mean you have to accept lavish gifts from them, and it sure as hell doesn't mean you get to lie about accepting those gifts. This is not about trying to control who someone is friends with, this is about a judge with immense amounts of power intentionally trying to hide that he's being influenced. Judge Thomas knows that this is immoral, and that's why he's been hiding it. That's why he should be impeached, because he's probably hiding a lot more, and the public deserves to know just how much he's been influenced by what is, effectively, bribery.
The person who gave him these gifts didn't have pending cases, but who did Judge Thomas meet while on these trips? Who did he have dinner with? Who was he introduced to while being wined and dined? "Technically I didn't give you this gift, but my very good friend did, and isn't it nice how we're having this very expensive experience while I talk to you all about politics, which just so happen to deal with the case you're about to oversee..."
A code of conduct for federal judges below the Supreme Court requires them to avoid even the “appearance of impropriety.” The SCOTUS should be held to an even higher standard. If Thomas doesn't have the strength of character to refuse bribery, then he shouldn't be on the court. If he wants to jet set around with rich friends, then he should resign from the court. If he wants to serve as a judge in the highest court in the land, then he needs to be above reproach. Some hospitals have made policies that doctors can't even accept pens from pharmaceutical companies, because even tiny gifts like that influence people. A $500,000 trip is going to influence someone a lot more than a Koozie.