It's unprofessional of him to tell you what to do, but that has nothing to do with him being 50-year old man. Therapists just aren't supposed to tell clients what they should or shouldn't do regardless of what they think of their choices. Therapy is not about giving instructions on how to live life but about helping people become more aware of their options and the consequences of their choices. The choice itself is always theirs, not the therapist'. It would've been much more professional of him to ask you about why breast reduction is important to you, to listen to what you have to say and to try to understand why you need it. He also could've asked about whether you are aware of the potential risks. His job is to understand that you are making this choice with the full awareness of what it entails and why you are doing it. But the choice is yours. You are an adult. You have the right to make choices in your life and you also are responsible for the consequences of your choices, meaning that you have to accept those consequences. Rights always come with responsibilities.

I am sorry you were treated like a kid by your T. You shouldn't have been.