I wouldn't feel badly about your reaction at all. It caught you by surprise, and it sounds like you envision the therapy process as maybe a bit more cool and distant--so this action would counter that.

ETA: I think it might be really fruitful, though, to talk with him about how you experienced the whole thing. Especially as you weren't feeling emotional about what you were saying, and his reaction being so different from yours. Lots of good material there to explore.