Isa, generally I believe your husband is expressing a very normal 'opinion'.
I think there are two sides to this emotional reaction and the one with the biggest impact is biological. One of strongest primitive drives is that of reproducing. The male strategy in the animal kingdom is generally to have a large number of genetic material (sperms) and spread them as often and with as many potential females as possible. He leaves the caring and most of the immediate upbringing to the female. His own assignment being that of protecting and bringing resources to the offspring (and female).
Now, if it turns out that he has wasted all this time with protection and resources on offspring that is not of his own genetic material, it has in an evolutionary perspective been a complete waste. This is, in a less subtle way, exemplified with several of the big cats, like lions for example. A new alpha male, taking over a group of females and their cubs, will often start by killing the cubs in order to start reproduction of his own genetic material.
I suppose, on a more or less subconscious level, this is still an unavoidable reaction with modern man.
As the female reproduction strategy is vastly different from that of the male, it is perhaps less of an emotional obstacle for a female.
Just some random thoughts, for which I am certain I will be kicked harshly and swiftly on the head.
