I, if you read the thread on marriage, am stridently against it. There is no benefit in getting married vs. having a girlfriend, only a huge financial risk. The legal contract gave her the go ahead to not work. As far as marriage goes, Judeo-Christian theology requires that in order for a marriage to be valid the couple must have an "openness toward children".
Still, guys need to take responsibility. What about asking for a pre-nup (no community property, no alimony)? She always intended to quit work, you ask for a pre-nup and you at least have some protection and it gives a window to her motivations (Is she getting married for love or are there parts of the legal contract that she really wants). If she doesn't work now, do you think she's going to put in the extra work that having kids will take (even as a stay-at-home mom)?
As far as the guy being turned down for a vasectomy, he should have gone to another doctor. Planned Parenthood could refer you to a doctor that believes in the "my body, my choice" philosophy. However, most guys don't realize that the majority of women want babies as badly as we want sex. More women than you would think would be willing to go outside their marriage to get pregnant.
There's nothing that you can do in that scenario except pay, its yours by law regardless of DNA. Even getting a vasectomy isn't enough protection if you are married, the law doesn't consider paternity fraud because it is still stuck in the age where an adulterous wife would receive brutal punishment. Besides, a vasectomy (if you haven't had a child already), violates the marriage requirement of "openness toward children"
I think guys know what the risks are, they just subscribe to the "it won't happen to me" line of thinking. I have heard of the term marriage strike, maybe there needs to be a baby strike until the law changes.