Your whole post didn't make much sense since you pretty much just said that emotions are what rationality is and argued from there.
So I just chose this one bit.
Why do bacteria procreate? Just because that's what they do. And so it follows that that is what every other living thing we know of does.
Rationality is not involved. Neither are emotions.
Rationalising whether to procreate is a human thing, and is just extra baggage. So are any emotions involved with procreating. When you get down to it, we just do it because that is what organisms do.
The emotions we feel during sex probably are there because otherwise there are too many other things we would be doing which would give us pleasure.
Because our brains are interested in stuff, while bacteria don't have brains really.
Not sure if I went off a bit there. I'm really unfocused atm. Maybe I shouldn't even post this lol