Understanding the text

"A Text cannot be made to speak to us until what it says has been understood" (Hirsch 18)

I totally agree that any kind of text is going to speak to us if we understand it. Obviously we are going to dismiss what we have read if we haven't totally understood it. I have another issue though. How do we know our opinions are right in the first place? Poems could say one thing to one person and something else to another person. Do we have to understand a text a certain way to really have us speak to us? For example in class I thought I totally understood what one of the critics was saying, (that the writer could be writing certain things to escape the current emotions of the moment) and Dr. Jerz made sure to tell me in front of everyone that I was obviously wrong. Even when we are wrong and we think we understand the text, the text still speaks to us.