How to Use Negative Questions When You Deplore Someone

The next area I want to touch on is negative questions when you disagree with somebody. Often if somebody gives an idea about something they want to do, you don't particularly agree with them. So how can you do that being a little bit more diplomatic? Because I'm British, I'm always going to see this through a British lens. For me, I'd much rather use a negative question to come back to something I haven't agreed with than necessarily disagreeing with somebody outright.