Here is another one.
My point isn't to attack your POV, I'm trying to explain that oxytocin has many well recorded 'bond' effects between people. It appears to support bonding between mother and child, romantic couples, and in reverse, reduce bonding between strangers.
If it works for self reported monogamous men, it's likely in effect with poly fidelitous men too. It's not like mothers kill their firstborn when the oxytocin helps her bond with her second child, after all.