There are basically two claims here:
1. Some corporate interests might want to secure sidechains for themselves and thus they will bribe miners to have these activated
First, it’s hard to imagine why they would want such a thing. Are they going to make a proprietary KYC chain only for their users? They could do that in a corporate way, or with a federation, like Facebook tried to do, and that would provide more value to their users than a cumbersome pseudo-decentralized system in which they don’t even have powers to issue currency. Also, if Facebook couldn’t get away with their federated shitcoin because the government was mad, what says the government won’t be mad with a sidechain? And finally, why would Facebook want to give custody of their proprietary closed-garden Bitcoin-backed ecosystem coins to a random, open and always-changing set of miners?
But even if they do succeed in making their sidechain and it is very popular such that it pays miners fees and people love it. Well, then why not? Let them have it. It’s not going to hurt anyone more than a proprietary shitcoin would anyway. If Facebook really wants a closed ecosystem backed by Bitcoin that probably means we are winning big.
2. Miners will be required to vote on the validity of debatable things
He cites the example of a PoS sidechain, an assassination market, a sidechain full of nazists, a sidechain deemed illegal by the US government and so on.
There is a simple solution to all of this: just kill these sidechains. Either miners can take the money from these to themselves, or they can just refuse to engage and freeze the coins there forever, or they can even give the coins to governments, if they want. It is an entirely good thing that evil sidechains or sidechains that use horrible technology that doesn’t even let us know who owns each coin get annihilated. And it was the responsibility of people who put money in there to evaluate beforehand and know that PoS is not deterministic, for example.
About government censoring and wanting to steal money, or criminals using sidechains, I think the argument is very weak because these same things can happen today and may even be happening already: i.e., governments ordering mining pools to not mine such and such transactions from such and such people, or forcing them to reorg to steal money from criminals and whatnot. All this is expected to happen in normal Bitcoin. But both in normal Bitcoin and in Drivechain decentralization fixes that problem by making it so governments cannot catch all miners required to control the chain like that – and in fact fixing that problem is the only reason we need decentralization.