I'm really upset. My dress is torn
will not usually be read as a passive construction, with torn as the past participle of tear. It will normally be read as a sentence that uses the adjective tear as a subject complement of my dress–similar to My dress is new.
If this answers your question, I'm glad. If this does not answer your question, I'm not sure what you're asking.
I think your question is
Since in the active voice the simple present refers to a general truth, as opposed to the present perfect, which refers to a specific action; why, then, does this not apply to the passive forms?
My answer is that this does apply to the passive forms.
But you have to make sure you are looking at passive forms to see that it does. Let's start with the active voice:
I'm really upset. I have torn my dress.
This states your emotion after the specific action of tearing your dress.
I'm really upset. I tear my dress.
In the context of reporting your present emotion, I tear my dress does not usually refer to a specific action. It could if it was a case of the "demonstration present" or "running commentary" present, when you can use the simple present instead of the present progressive to report what you are doing right this moment. But this is a special usage of the present tense.
So, one can take the meaning of I tear my dress here as referring not to a specific action, but to a general truth, especially in the sense of a repeated or habitual action. This is clearer if we join the two sentences:
I'm really upset when(ever) I tear my dress.
Here, now it's also clear that I'm really upset also does not report on one's present emotion but states a general truth. A caveat to this is that you can say this statement as a statement of general truth when you are experiencing one instance (occurrence) of this general truth, that is, of tearing your dress.
Now, for the passive voice (or passive constructions).
I'm really upset. My dress is torn.
This sentence can be read as a passive construction; but it doesn't have to be.
In fact, without an agent stated with by, this sentence would usually be interpreted as using torn as an adjective (not as the passive form of tear).
In this case, the two sentences report your present emotion at/over the current state of your dress. Here
My dress is torn
My dress is new.
Both torn and new are adjectives, acting as subject complements.
To make it clear that My dress is torn is a passive construction, you could state an agent, as in
I'm really upset. My dress is torn by the dog.
Now, you are in the same situation as the active construction. And this can be taken as a general truth:
I'm really upset when(ever) my dress is torn by the dog.
But without an agent stated, and without any context My dress is torn is unlikely to be interpreted as a passive construction.
As for the present perfect passive
I'm really upset. My dress has been torn.
The most natural way to read this is as a passive. When you do this, this is not stating a general truth but reporting your present emotion about the specific past action of your dress having been torn by an unstated agent. Again, you could make the agent explicit by adding by the dog.
But, again, you could use the two sentences to report a general truth if you combined them:
I'm really upset when(ever) my dress has been torn.