> Why do you believe a slider would force people not to share misinformation? There must be some basis for that opinion.

"Force" is a strawman, but there is a clear basis for thinking that an accuracy slider could cause people to be more thoughtful about sharing: the results of this study, which found that "subtly inducing people to think about accuracy" resulted in "participants in the treatment group were significantly less likely to consider sharing false headlines compared to those in the control group, but equally likely to consider sharing true headlines". The effect found was quite significant.