It’s not “destroying all the enemies of the working class” but “destroying classes so we end up being working class”. The idea (as I understand it) is that working class is the one that creates things while bourgeois class is only a parasite. So everyone should be creating something and not sucking the blood of others.
Maybe I didn’t explain myself correctly. For the bourgeoisie class to disappear it’s not needed to kill anyone. Only take off the power they have and make them work as proletarians.