Historical revisionism is the name of the phenomenon in which one revisits, reexamines, or attempts to revise the established or commonly-held view of historical events. This can be beneficial to the study of history when the conclusions reached are fact-based and follow the scientific method; or negative when they rely on incorrect, selective, or manipulated data.
The label 'historical revisionist', much like 'conspiracy theorist', is often used by people (whose method of "historical research" is skimming Wikipedia articles) to dismiss different perspectives without examining the evidence for them.