The Question and Answer section for An Inspector Calls is a great resource to ask questions, find answers, and discuss the novel.
Although this quote sounds famillar, I've just scanned through the text and I can't seem to find that exact quotation. I would suggest that it is Arthur Birling who says this given the context but I cannot see the quotation currently.
You will have to scan your text for particulars but the inspector is known for his almost supernatural ability to know a character's motivations and encourage confessions.
I think if Eva Smith had a talking part, she would be sympathetic to system was more fair to her.