in this sentence both would be correct. If you use "tobie" there is more stress on that word.
Tobie is used in accented position, ( beginning of the sentence, after preposition, end of a longer sentence, and if you want the word to be accented).
Ci in not accented position.
Just a comment: I do not think that the dative plural of you has appeared in any lesson up to this point. Since you can hover over and get the missed information, it's not a huge deal, but it's a little inelegant.
Does ufac always take the dative, or is there another rule I need to be aware of here?
Wrong case. "ufać" takes Dative, which is "tobie". "ciebie" is either Genitive or Accusative.
So usually a negative sentence takes genitive, but ufać overrules this because it always takes dative.. Is this right?
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.
why it is not being translated as" we do not believe you" or cannot be translated so.
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.
Yes, it's the 'stress' thing. Both can be Dative, but actually "Nie ufamy ci" would sound a lot more natural to me. "Nie ufamy tobie" is like "We don't trust YOU".
It is a common mistake when polish people overuse these long, accented forms "tobie, ciebie". They want to be considered well educated I think. But in fact it sounds really, really pitifully and hurts the ears.