You're absolutely right
That makes sense
I'd go along with that
I agree with you up to a point
I couldn't agree more
I'm afraid I can't go along with that
I'm not so sure about that
I'm sorry, but that's totally unacceptable
You can't be serious!
I'm not sure I would agree with that
I'm sorry, but there's no way I could accept that
I see where you're coming from but...