Of course you can cease argument without consideration - if you deem the risks of continuing consideration to outweigh the benefits of weighing them. For instance, if you have 1 minute to try something that would save your life, and you require at least 5 minutes to properly assess anything further, you generally can't afford to weigh whether the idea would result in a worse situation somehow - beyond whatever assessment you have already made. At that point, the time for assessment is over.

For the most part, however, I agree with your point. I did not argue that one can rationally disagree with the statement "We need to balance the risks and opportunities of AI"; just that they can sincerely say it, and even argue for it. This was a response to you saying that "no one would ever utter the phrase in the first place". This just strikes me as false.

Never underestimate the power of human stupidity ;)