Individual instance owners can block Meta instances from federating (exchanging data), and they absolutely, 100% should do so. If enough instances block Meta, it'll be like they don't even exist.

The bigger issue is that corporations can present a united front, while federations cannot. This is why hegemonic forces tend to win; as the author says, there's already division among kbin/Lemmy users about whether blocking Meta is a good idea. You can be damn sure there isn't similar division among Facebook leadership about whether to destroy kbin/Lemmy.