It may seem confusing that Nietzsche might see the ascetic ideals of the herd as in some sense good for them. No doubt, Nietzsche despises the herd, their morality, their weakness, and their ressentiment. He even claims explicitly that ascetic ideals are harmful. However, if we recall section 13 of the first essay, Nietzsche would not blame the herd for being the way they are. It's not as if they could have been strong and have failed, making them somehow responsible for their weakness. Rather, they simply are what they are, with no sense of guilt or responsibility attached. Nietzsche's low esteem for them is thus more of a "sucks to be you" than a "you should be other than you are." The herd doesn't have the option of being strong, and so for them, ascetic ideals may be the best alternative. Nietzsche's main objection at this point is that these ascetic ideals have become so dominant that they have poisoned our entire species and harmed some healthy spirits that have no need of slave morality.