Can I send a letter to my husband's boss?

My hu*****and is lack of social skills. He did not like any social conversations and very frank and naive.

A couple weeks ago, he pointed out some things for his boss's presentation in the lab meeting while his boss invited everyone criticizing her presentation. However, my hu*****and got an email from his boss asking him to find another job somewhere. My hu*****and then realized that his talk at the lab meeting offended his boss. He wrote an email to explain that it was just academic discussion and also asked for forgiveness from his boss but on the day before Thanksgiving, his boss still informed him that she would not support him from January.

It is a shock for my family since we just submitted Eb1b( Green card application) this summer, what else can we do to change the boss's decision? The boss is a Caucasian lady. Is it appropriate for me to write a letter to her?

Thanks