Why does Melinda consider Mr Freeman the sanest person she knows?

Mr. Freeman is Melinda's art teacher. He refuses to grade the students and instead keeps track of the students' progress in a table painted onto the wall. He calls this "a necessary compromise." Mr. Freeman's reluctance to blindly follow rules passed down from "the authorities" seems to Melinda eminently more sensible than the unquestioning acceptance of many of her other teachers. This is one reason why Melinda respects Mr. Freeman, and thinks of him as "the sanest person" she knows.
Mr. Freeman is also a very creative, abstract thinker. He tells Melinda that "when people don't express themselves, they die a piece at a time." Mr. Freeman expresses himself and speaks about art very candidly, emotionally, and enthusiastically. For example, when a student asks him about the picture he is painting, Mr. Freeman replies that the painting represents "Venice at night, the colour of an accountant's soul, a love rejected . . . the blood of imbeciles . . . the taste of iron." Melinda, overhearing this response, says that "some teachers rumorwhisper he's having a breakdown." The implication here is that Mr. Freeman's manner of talking, combined perhaps with the aforementioned indifference to authority, is interpreted by his colleagues as at best eccentric and at worst something approaching a breakdown. Melinda realizes, however, that this interpretation says more about Mr. Freeman's colleagues than it does about him. Melinda interprets Mr. Freeman's manner of expressing himself as honest and sane.