Not exactly. Unfortunately many people take the rule too far.
The rule is "a sentence that took Accusative takes Genitive instead when it's negated". Not 'any sentence'. Other cases stay the same when negated.
Also, if the sentence took Accusative because of a preposition and not because of a verb, Accusative also stays even if negated.
Ufamy ci but Nie ufamy tobie. Looking at the discussion Ufac takes dative but isn't my example two different cases? I am aware of a difference in case use like Ja mam... nie mam... Can someone simply define the grammar of my example? Meaning Ci is whatever case with ufac and tobie is whatever case possibly due to negation? Unless it is just stressed as mentioned in the forum? The less "why" the better. I just need to get it straight so I can practice.