I’m sure that Mrs. Hudson’s husband committed a great number of crimes in order to get sentenced to death. From the way she flinches when Sherlock slams his hands on the table, I’d say it’s safe to bet that one of his many crimes was spousal abuse.
That would certainly account for why Sherlock ensured his execution.
And why Sherlock got so enraged when he saw that she had been hurt
And why she acted as if she were perfectly fine when she was hurt.