but I wonder if a problem with open relationships involving couples planning on having kids is that the man might (for genetic reasons) care less for a child even if he knows with certainty that the child is theirs.
Yes, until recently it was impossible to know with certainty that the child was his.
And even today feminist organizations are doing their best to keep it that way. For example, they managed to criminalize paternity testing in France.
they managed to criminalize paternity testing in France
By that standard, sex is also criminalized in many countries -- after all, it's only legal if the participants consent.
Personally, I'm not a big fan of the French law, but your interpretation of facts seems a little... creative.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.