Can you tell me how to deal with people who bring up unsourced things that I feel aren't (fully) true, or are "fake news"? I agree that I can sometimes get stuc

Can you tell me how to deal with people who bring up unsourced things that I feel aren't (fully) true, or are "fake news"? I agree that I can sometimes get stuck in a discussion, but I also feel like it's harmful to let unsourced claims spread. In this thread I mostly wanted people to source the claims they were making, and for that I got downvoted and called a shill. How should I approach this in the future?