The less you remember, the more open is the gate for the next one like him to show up. It's for a similar reason that Germans very much do make sure the Nazis aren't forgotten about, e.g. Let him have his fame in history books.
As an example of what to avoid and how to avoid getting someone like him back.
The current trend of nationalists who willingly adopt the Nazi theme and name is strong and everyone remembers Hitler very clearly. The problem is that the name is also shorthand for other Nazi bullshit. The message of nationalism is clear - teach the subject, show how it works and what to look out for, and attach no person to the ideology to undercut any culture growth around the celebrity.
The surest way to deter fascists is to make the losers look as uncool as they are by making fun of them. Even small nothing statements get under the skin of the dictators so be juvenile and save history.