(a) is underspecified. Benefits you according to whose values? If it's someone else's values, then I would object. If it is your own values, then whether it benefits you really becomes secondary, because what matters is that they need your consent. Whether you give consent based on what benefits you is not a primary concern, though presumably you would.
(b) seems to me like an expression of a naive view of personal identity that makes a binary distinction between anonymity and non-anonymity that doesn't exist in reality in any meaningful sense. Does manipulation against your interests become a non-problem when the manipulator doesn't know the name in your passport? Does it become a non-problem when the manipulator's tools are too imprecise to pick out you specifically, so they apply the same strategy to you and one other person, yielding only a 50% success rate? Does it become a non-problem when they lump you in with three other people? With four? Ten? A hundred? A million?
All of this is about power. Just because power is exercised indirectly or somewhat imprecisely doesn't make it categorically different from someone influencing specifically you, just as poisoning rivers and lakes isn't categorically different from poisoning your food on your plate. It's just a scheme for laundering the power to make it less obvious, and if you allow that, that's what people will do. People who want power don't care how they get it, all they care about is that they get it, so if you tell them that you are OK with being manipulated indirectly, then that's what they will do.