Life is not fair. However, this is a false equivalence. Do you support that wages are garnishable to pay off debts? Would you support a law that put a person into indentured servitude to pay off debts? Assuming the answer to the first is "yes" and the second is "no", you are making a distinction between the level of legal auythority over a person's property and over their body. That same distinction applies here.
I think you're missing the point, sort of. If a man and woman have unprotected sex and conception results the woman has a full array of options. She can chose any of them, only the man who she conceived with can be hugely impacted by the decision she makes while having no authority over his own course of action.
If I accrue debts then I am obligated to pay them off, one way or another. How would you feel if when a married couple accrued debts the woman could decide to cancel the debts if she felt like it but if she didn't cancel the debts the man would be obligated to pay them. Also, if the man wanted to keep the debts, because he wanted to keep the stuff he acquired through that debt, but the woman decided to cancel the debts and have all the stuff repoe'd even though the man was willing to pay for it all.
Yeah, life's not fair, but it makes sense to look at it and ask why it's not fair and if maybe it could be made fair, right?