That's not how this works at all.
Slashing happens under a very specific circumstance: a staker submits contradictory messages. Those circumstances are testable with built-in code that's part of the protocol. To get someone slashed, you send a transaction including their contradictory signed messages. When your transaction is included in a block, the staker gets slashed by the protocol rules hardcoded in all the consensus clients.
The only other thing that can cause a staker to lose stake is the "inactivity leak," where an active staking node doesn't send the messages they're supposed to send. That's completely automatic.
You are basically stating that slashing is impossible in certain conditions because network is not censorship resistant.
There is one avenue where network can censor. It is a 51% coalition that orphans blocks that contains slashing txes. This coalition is dealt with UASF (user activated soft fork), since this type of behavior goes against core principals of the network and convincing people to do it will be really easy.
That's not what slashing is supposed to be used for, but if that situation happened again, Ethereum would fork again, just as last time when Ethereum classic didn't agree to freeze the Ether from the DAO hack. PoS makes it a little easier to fork (which is good imo), but doesn't change anything fundamental. Everyone still needs to be in complete agreement about the rules and history for Ethereum to work.
Validators are run by people who fully control if a transaction is valid or not. You either need a ton of GPUs (currently) or a ton of money to have tangible influence over translations.
This isn't even a hypothetical, there's a few massive wallets that are hoarding a ton of eth that will be given more power from the POS transition.
We're relying on "the goodness of their hearts" validator operators and crossing our fingers validators run the same software with the same rules.
Even if you call out sketchy transactions that are close to 50/50 consensus, nothing will happen unless a ton of people have a ton of money on the line like the DAO split.
We need more discussion on how incentives of each party should be to give the most stable network possible.
It's not as if they're automatically given more power. Such hoards of ETH would need to be deposited in units of 32 ETH to activate unique validators. You could have a large number of validators that are actually a single computer program participating in the Beacon chain, but that doesn't make too much difference.
At the bottom layer, we're talking about the application of an open p2p protocol on the Internet. People can and will analyze the traffic for that protocol, and it will be possible to identify rough shapes and sizes of players in the network. And such analyses won't be long in coming to public blog posts, etc. following the Merge.
If decentralization in the network seems at risk, there will be efforts to remedy the situation. Whether they can succeed is another question.
edit: for an example. you get hacked and lose $100M. You say fuck it, submit a slasher report that says it wasn't a valid transaction. you offer enough money to get x% of validators to agree with you.
As far as I can tell, you cannot get slashed for your vote on a slash. So lying is ok.