But sure the antique Greeks were far more mild, Else of our Sex, why feigned they those nine
In order to defend herself, she goes right back to the muses, and to ancient Greece, which, as we've already seen, are two recurring themes in this poem.
She uses the Greeks to poke fun at prejudiced male readers. Why, the speaker asks playfully, would the Greeks have made ("feigned") the muses themselves women if they thought women were such crappy artists? Ha! Bradstreet 1, Jerks 0. Sorry, we kind of have a tendency to root for her—we'll try to keep it under control.
Special poetry bonus points if you noticed the internal rhyme with that long E in "antique" and "Greeks." Cool, huh? If you just shouted out "You betcha!", get yourself over to "Form and Meter" for more of that good stuff.
And poesy made Calliope's own child? So 'mongst the rest they placed the Arts divine,
Just for good measure, the speaker throws in one more little dig about the ancient Greeks. In this line she points out that the muse of epic poetry, Calliope, was herself a woman, taking her place among the other arts.
She didn't really need to add that last allusion, since all the muses were women, but she seems to be kind of enjoying needling her opponents now.
It's also worth pointing out the personification of poetry (she uses the old-fashioned term "poesy"). Bradstreet's speaker turns an idea, "poetry," into a person by referring to it as a child.
But this weak knot they will full soon untie. The Greeks did nought but play the fools and lie.
Having brought up this good point, she puts it to rest, imagining what her opponents will say. She doesn't imagine they will have any trouble with this "weak knot" of an argument. Notice, by the way, how she picks up on the theme of female weakness she brought up before when talking about her "weak brain" (line 24). Her critics' cutting response seems to boil down to, "The Greeks were dumb and full of it"—not exactly impressive.
The reader is left to pick up on the difference between the speaker's calm, patient voice and her opponents' foolishness. It's just another echo of the gentle ironic tone that runs through this poem.