Big "guns don't kill people, people kill people" energy.
Facebook has the resources and personnel to maintain basic ethical standards for whom they sell their products to and how they are used. They chose not to because it is more profitable to chose not to. This isn't either/or. You blame the operators of those websites AND you blame big tech.
We need to stop pretending it is remotely OK to behave without any semblance of humanist morals in the pursuit of capital. It isn't. It never was. It never will be. Anyone who tells you profits need to be prioritized over ethical standards, in any situation, at any time, for any reason, should be committed.