Why do people bash single mothers but give deadbeat fathers a pass?

I especially see men do this the most. Even in cases where there are single fathers or even men who are stepfathers, they're viewed as good men. However, the moment a single mother is brought up, she every name in the book and is almost always immediately blamed for the actions of the man. Why is that? What makes it different?

Why do people bash single mothers but give deadbeat fathers a pass?
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