'Do unto other as you would have done unto you'
It is fallacious. It is a claim(That you *should* do unto others as you would have done unto you) This has the underlying premise that what is true of you and your worldview is true of others.
Not only does this rule ignore personal differences, that people do think diffent than you, it supposes that others should think like you, and it justifies the Reaction Formation.
My favorite example of the Golden Rule is Roy Cohn, a politically connected lawyer who was gay and died of Aids, but who viciously persecuted gays during the middle 20th century because he was too cowardly to accept himself as he was.
It's something that is very commonly used in arguments on all sorts of topics, and I personally think that there should be a fallacy called the Golden Rule Fallacy, created as a subcategory of the anecdotal fallacy.