When in reality, it's just them projecting their own view. Libs or the media do it all the time when "defund the police" comes up. They say "well, it just sounds like you're getting rid of the police entirely and your messaging is off. Its gonna turn off people in middle america." or something.
I think there was a segment of a Citations Needed episode that talks about this.
Don't overthink it. Demand that they tell you why they believe what they believe. More often than not, there's no argument. Who, specifically, will be turned off by X? In what way? What would be a more effective way of addressing X? You're right, there is no point, so ask what their point is and force them to either concede or out themselves as polite conservatives.