By letting them do it. Hillary did it to day and did it well. Scream; accuse your opponents of bad motives/racism/stupidity/whatever to diminish the value of their opinions to the public dialogue. And most of the conservatives today won't stand firm. I remember when some deadbeat angrily demanding that a campaigning Ronald Reagan explain: "What if I'm opposed to you cutting public assistance benefits like you say you will?" He replied: "Then I'd suggest you vote for someone else."