I would be happy to help you with your question. Please answer these questions so that I may better help you.
What are your ages?
Have you talked to him about how much his behavior bothers you?
Has he always been a critical person?
Do you know if he is depressed or angry about anything in particular?
What exactly would you like my advice about?
There could be any number of reasons that a person speaks critically of others. Often times, people use criticism to mask their own feelings by focusing on the problems of others. It sounds like your boyfriend becomes very defensive when you confront him about his behavior. In fact, he may become more critical when he feels like you are "fighting" with him. Also, people may become critical when they are holding in negative feelings and refusing to talk about it. Given his age, it could be possible that he is experiencing a problem with life-cycle transition. That is, as he becomes older, he is becoming increasingly aware of the reality of his life choices. He may be angry about choices he has made in life and it is just easier to take it out on someone else. Regardless of the reason for his behavior, it has negative consequences. He may benefit from seeing a therapist; however, I seriously doubt that he would agree to therapy. You may want to encourage him to sit down and talk with you about what is bothering him. You could ask him why he feels better when he criticizes other people. Explain to him that it is hurting you and making you feel uncomfortable. Maybe this will motivate him to share some of his feelings. I would not get my hopes high, but I would certainly give him the chance to explain his behavior. If he refuses to talk, you may want to try ignoring his criticism. Reinforce his positive behavior by giving him compliments about what he does well. Tell him how proud you are of him and how much you respect his hard work. If you ignore the negative and reinforce the positive, he may start reducing his critical behavior.
If you found this answer helpful, please click accept so that I get credit for my work. Bonuses are greatly appreciated. Thanks!