***** NOT A TEACHER *****
Hello, Kiann:
May I add a few words to Tzfujimino's excellent answer?
One of my favorite books * says this:
1. He is the man who we thought should be censured.
a. "Who" is the subject of "should be censured."
b. As you said, "I believe" is a parenthetical expression.
2. He is the man whom we thought you should censure.
a. "Whom" is the object of the verb "should censure."
i. ONLY MY NOTE: If you put the sentence in "regular" order (subject + verb) for analysis (of course, do NOT speak like this), you get:
"He is the man we thought you should censure whom."
James
*Walter Kay Smart, English Review Grammar (1940; copyright renewed 1968), page 30.