I agree with you about the power imbalance problem. But to the extent that there is an equivalent slur toward men, I think it would be something like "dick" or

I agree with you about the power imbalance problem. But to the extent that there is an equivalent slur toward men, I think it would be something like "dick" or "prick" rather than "bastard". Those are words that are derogatory in a gender-specific way, specifically directed at males.