What grounds did Nehemiah use to justify his imprecatory petition?

Note that Nehemiah focuses not on himself or his people, but on God himself: For they have provoked you to anger in the presence of the builders. Sanballat’s and Tobiah’s derision blasphemed the Lord God, and that injustice must be vindicated. Those who dishonour the very people whom God has honoured (adopted in his covenant to be his people) dishonour God himself. Here is the same emphasis as is found in the first petition of the prayer the Lord taught us to pray, Hallowed be your name. That they did so publicly only heightens the need for (public) vengeance.