In Ezekiel's poem, the scorpion serves as a metaphor for an overbearing fear. The scorpion in the poem does what scorpions do. He stings the mother because she got too close to him. However, the hunt and the fear that comes from the scorpion represents a powerful force that could be related to fears we feel in life. Ezekiel may have had something specific in mind, but whether he did or not, a reader can take the poem and make it represent something that is relevant to their own lives.
The fear and hunting that occurs in the poem is similar to the fear created during the Salem Witch Trials. The people "came like swarms of flies/ and buzzed the name of God a hundred times/ to paralyse the Evil One." They've represented the scorpion as evil and they've created an irrational fear of it. Keeping in mind the Salem Witch Trials idea, you can see by this line that they are unable to find the scorpion:
With candles and with lanterns
throwing giant scorpion shadows
on the mud-baked walls
they searched for him: he was not found.
While a scorpion isn't impossible to find, it is very difficult. Similarly, finding the "witches" was difficult. In each instance, the fear comes from the differences and misunderstandings between the two parties.