Why did my advisor criticize my work for the first time at my Master's Thesis defense? I had two advisors for my master thesis. One, as my first advisor would take the theoretical part to guide me. I have been meeting with my first advisor once every two week and he has been examining each part of the text. During these meetings, he continued to tell me how good I am doing and I should keep writing in this way. There were never real feedback, which could be pointing out my mistakes. 

So I developed a full confident in myself and in the work. He offered me that I should consider starting a PhD with him.  In short, during the time I have been writing my masters thesis, he gave me all signs that he approves and likes my work. 

My presentation took place a week ago, and was pretty much successful in my opinion and in the opinions of other people who came to listen. But at the end of the presentation, I received a totally different attitude from my first advisor. He started to criticize the work in a way he has never done in our meetings. 

I was shocked about how my first advisor could not defend me and his own ideas in front of the committee and I am incredibly disappointed. Not only have I lost my belief in him and his judgments but also, I am now doubting my own skill of writing. 

I am going to meet my first advisor next week and planning to talk about his twist of judgment and criticism. In this talk, I will question the PhD idea. I'm not sure though, how to put my anger, disappointment in right words, without making him feel that I am attacking to his personality. Also, when I asked him if we can meet earlier than next week, he refused. I have the feeling that he knows what i am going to say and now trying to construct a distance. 

I know that trust is a very important issue in between the advisor and the advisee. If we will continue work together, I have to ask him an explanation but as I said, I'm afraid of my own frustration and if I cannot express myself in a right way.

My question is, would it be wise to express my disappointment in him, especially now that we will start to focus on my PhD? On the other hand, I need him to justify his inconsistency, which is quite crucial for me to keep working with him.
You cannot go after him for asking questions, that's his prerogative. You can choose to work on your PhD with him, or without him. That's what the conversation ought to be about.

Check out Crucial Confrontations:
http://www.frumi.com/images/uploads/CrucialConfrontations.pdf

With a crucial discussions like that, it is always good to give yourself a pep talk and imagine why would a rational being do something like that. Was is really that bad? Were you his first student, and was he nervous? Could he have had some personal issues to deal with? Perhaps he feels embarrassed for his behavior? 

That will help you develop compassion and temper your anger (regardless how justifiable it might be). The goal is really to channel your emotions.

Then you are ready to develop a focus for your discussion. You can pose it as the discussion about your concerns about doing PhD with that advisor. Let's face it, you were not going to do PhD with him, there wouldn't be need for the conversation. Ask questions, at this point.

For example, I was surprised with the level of question received during the defense. I was left doubting the quality of my work, and now I am concerned about proceeding with PhD because my work is not as good as I thought it would be. What is your take? That should be enough to start the conversation without accusations. 

Keep in mind, they are supposed to ask you hard questions at the defense, it is an exam. It might even be a compliment - he wouldn't have asked you these questions, if he didn't think you can handle them.  My advsor holds practice defenses. The labmates and the adviser ask hard questions then. For my defense practice, I was answering questions for an hour! If it wasn't for the practice, these questions would have come at the defense time.