What "rights" do fathers have that need protecting? I think it's mothers' and babies' rights which need to be protected myself.
"I don't agree with your opinion that because he wasn't interested in becoming a father, that he automatically would not be interested once that actually happened."
Well that's pure speculation on your part. What we do know is that he had no interest after they had sex.
"Women who become pregnant unexpectedly (and their partners for that matter) don't automatically have 'less interest' in the ensuing pregnancy and child. To assume so is rather offensive."
I don't assume anything about women. Please don't put imaginary words into my mouth and then take offense at them.
"I don't believe you seriously expect that after every episode of sexual contact between a man and woman, whatever the relationship, the man should check whether the woman has conceived...."
Well like I said if he wants to demonstrate that he does have an interest in any children he may have helped conceived then yes it probably would be a good idea. Whether he does so is up to him but people can draw their own conclusions from his behaviour.