ideally as human beings we did not evolve to workout at night obviously.. if we did then we would be like cats, rats, and possums and be able to see at night and sleep during the day.
however in modern society we managed to fuck things up and a lot of people work jobs where they work at night.. we have seen plenty of evidence that people like this live shorter lives and have much more health issues as they age.
so ideally working out at night is not a good thing, BUT if you gotta do it then oh well.