If we understand classism to be prejudice and oppression coming from one class toward another (despite all the vagaries involved in deciding who's in which class...), then it makes no sense to think of classism as anything other than what ruling class and middle class people do to working class and poor people. Ruling and middle class people are the ones who have access to institutions that are capable of manifesting prejudice and oppression, while working class and poor people do not. It's really that simple. So whatever class hatred might exist among anarchists, it's there for specific reasons that can be seen and measured. It's convenient for anarchists to despise "the rich and privileged" (whoever they might be), and it may even seem unreasonable at times, but it's not "classism" to hate the people who exploit and oppress you.