Here's another analogy:

A homeless person asks for money. You don't give him money but give him some advice. Can the homeless person rightfully criticize you?

You can absolutely criticize choices made by volunteers. I don't think you need to think too deeply about this to imagine situations where few would object to criticizing a volunteer's behavior. An obvious one would be if an open source maintainer willfully included malware/etc. into their project - which, to many people, ignoring glaring security issues is vaguely equivalent.

I obviously don't think vitriol is warranted ever, but criticism obviously is from time-to-time.