If you want to stop a conversation dead in its tracks, use the word “but.”
I read a number of years ago a suggestion that we use the word “and” in place of “but” when we are involved in substantive dialogues. The idea behind using “and” instead of "but" is to keep the discourse open rather than trying to stop the idea or the expression of a position by another person.
I’ve tried it, and it seems to work. Another strategy I’ve tried using to train myself away from using the word “but” is to pause briefly after another has expressed their thinking/position/idea, then offer a question for consideration. Instead of the using the word “but,” the question I offer generates more dialogue and freer exchange of ideas. The questions I choose allow me to introduce a counter-perspective as a possibility for discussion, rather than a direct rebuttal to the other person's idea/thought.
Reducing usage of the word "but" really has been beneficial for me. It does seem to keep conversations going and the doors of possibility open.
Try it. See what you think.