Respectfully, I disagree
Want to be able to disagree respectfully? Two things to keep in mind:
Make your intention to learn and relate, and
Don’t make it personal.
An easy way to do this is to avoid the word “you,” as is in “You’re mistaken/wrong/dumb…”
Instead, you can say, “I don’t see it that way. Can we discuss our different views?”
This creates a mutual purpose: discussion.
Or, you can start by seeding doubt, or softening the blow, rather than launching in with a forceful rejection.
When someone says something you disagree with, you can reply with a simple, confidently stated: “Are you sure?” or “I don’t know that it works like that” or "I don’t know that I see things that way. Can you explain?"
Then just be quiet and maintain eye contact (in a neutral way), to allow that doubt to sink in.
Remind yourself that your intent is to learn and connect, not to punish or make the other person wrong.
This will have a better chance at dialogue than "I don't get what you're saying," or "You don't understand."
Remember that disagreements are inevitable, and OK. When you don’t express your feelings and needs, resentment builds.