Any statement that claims to need no proof or support for its claim because it is so obviously correct. This is similar to an ad hominem; however, nobody is directly attacked... unless he/she chooses to join the group of self-evident fools who would dare go against the initial claim. In self-evident truths, an assertion includes a phrase that will make the listener feel intellectually or morally inferior if he/she does not agree with the assertion. In a way, a self-evident truth fallacy is like a preemptive ad hominem.
Red Flags:
Everybody knows... No one can deny... Unquestionably...
Anyone who has any sense... It is only too clear that... What fool would agree to...
Example: Only a fool would deny that Mr. Spagnolo's classroom is the nicest room in the building.
Anyone who disagrees will appear to be argumentative, and, if everyone else agrees, the one who disagrees might be looked at as a fool.
Example: Anyone who has any sense at all knows that Timbuktu, not Bamako, is the capital of Mali.
It's not the capital, Bamako is, but I just made you reconsider or simply agree with me because you didn't want to appear senseless.