Author identity

An issue that was raised in class a few weeks ago: how important is an author's identity to a poem or story?

We're taught to separate the author from the speaker in a poem or story. This is easier to do when it's a work of fiction --after all, the genre itself says that the story is "not true". But what about a poem? Do we assume the speaker is the poet or not? Is it a case-by-case basis? When do we know that a poet's identity should or should not inform one's reading of a poem?

Here's an example:

"Pulled Over in Short Hills NJ, 8:00 AM"

It's the shivering. When rage grows
hot as an army of red ants and forces
the mind to quiet the body, the quakes
emerge, sometimes just the knees,
but, at worst, through the hips, chest, neck,
until, like a virus, slipping inside the lungs
and pulse, every ounce of strength tapped
to squeeze words from my taut lips,
his eyes scanning my car's insides, my eyes,
my license, and as I answer the questions
3, 4, 5 times, my jaw tight as a vice,
his hand massaging the gun butt, I
imagine things I don't want to
and inside beg this to end
before the shiver catches my
hands, and he sees,
and something happens.

--Ross Gay, Against Which

Many of my students read this poem as someone being pulled over, perhaps for getting caught speeding, and the physical experience of that. No one paid attention to the town named in the title (even though most of my students are from Jersey... though, how many of them have heard of the town, one known for its affluence? I can't say.). One student suggested that the speaker was late for work, indicated by the time mentioned in the title, and was speeding. There was no mention of the poet being a black man, because, really, is that relevant? But in light of this, knowing the color of the poet's skin, does this change the reading of the poem? Of course it does.

So how do we, as readers, know when to take a poet's identity into account and when to ignore it? There are no hard and fast rules to follow, but how do we determine how to read a poem?