First, take “dads” out of that sentence and replace it with “parents”. The obligation of support falls on mothers and fathers alike. Secondly, I’ve already made the argument why parents of a child should be expected to shoulder the burden of childrearing repeatedly. If you want to see it, scroll up. You’re the one arguing that the parent who does not wish to comply with the law has a right that is being trampled; I repeat, the burden of proof is on you to show how what this right is and how it is being violated.
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An innacurate statement of the law and a false analogy to boot, although you are correct to say it has nothing to do with anything. “Assumption of the risk” has a specific legal meaning in the law of negligence; you assume the risk of injury engaging in a hazardous sport. You don’t assume the risk of assault by going outside. Use of the phrase outside of that context is just plain wrong unless you’re attempting to analogize to the law of negligence. Moreover, both are tortured analogies. Pregnancy is in a “natural and probable consequence of intercourse”; it’s what the activity is designed to bring about. If you don’t want to suffer the natural and probable consequence, don’t engage in intercourse.