On the other hand, Joth, scum knows they're telling the truth, so they're going to think twice about going out against it.
I take it you didn't follow Dice Mafia, but on Day 4, Beyond Awesome and Myself were made Masons, with scum!Arch and scum!Lio alive, as well as town players Faust, Ash, PPS, Hydrad. The three players that questioned the claim on Day 4, and were pushing to lynch me, were Faust, Ash, and PPS, all town. Lio and Arch immediately supported our claim.
The situations were somewhat different there, as previous interactions in the game affected people's interpretation. But still Lio and Arch didn't want to go on the record as painting our claim as false because they didn't expect anyone else to question it.
So, scum has some motivation to strongly support a claim they know to be true.. precisely for what's happening now; questioning it gets a lot of scrutiny.