If someone is half serious and half joking, and it isn’t very obvious which parts are jokes and which are not, that leaves him in a position where he can act as though something is serious up until he gets called on it, at which point he can switch to saying “of course that was bad logic/bad sources/ad hominem/etc., it was just a joke?” So you’re better off acting as though it’s jokes all the time.
If someone is half serious and half joking, and it isn’t very obvious which parts are jokes and which are not, that leaves him in a position where he can act as though something is serious up until he gets called on it, at which point he can switch to saying “of course that was bad logic/bad sources/ad hominem/etc., it was just a joke?” So you’re better off acting as though it’s jokes all the time.