If FLoC is what I have understood it to be then, I support it.
Two things in FLoC's favour: The algorithm is open-source and it's client-side.
It would be trivial for developers of ad-blockers to provide tools for anyone who cares about privacy to inject poisoned data into their stream. And for those who don't care, well it's a market and they are free to choose to partipate or not.