More can be written, but you might like a previous discussion, "To what extent is Grover Furr's account of the Moscow Trials supported by third party research?" . That is a specific case, with debunkings by /u/fragmentedmachine and commiespaceinvader, but /u/kieslowskifan also points to more general debunkings by /u/International_KB .

This is not to discourage discussion. More questions, data, and debate are welcome.