This one feels less sinister than some other things at least to me, personally. You can reasonably doubt that the conservation of mass is violated and find out the truth based on that. But understanding more complex biology or historical context for some things? Granted, many of these things seem to be low stakes, but I'm sure there are some there are not (sex ed comes to mind).
to be fair, fusion does violate conservation of mass, just not the way the teacher explained it. the loss of mass is where the energy comes from.