Providing feedback to teachers can be a tricky prospect at times. Teaching, and instruction in particular, is a very personal undertaking. Getting up in front of a room of children takes a great deal of nerve at first, so as teachers become more and more accustomed to it, they tend to become more and more fixed in their approach to it.
This is a generalization, of course—not all teachers are like this. Some of the best teachers I have worked with love feedback and work hard to reflect upon and improve their instruction.