Theoretically I can stand up a mining operation in my apartment. That means that the 51% attack (as long as it can be detected) can be thwarted by folks at the grass roots level (as long as they actually care). Am I wrong about this?

You are practically wrong about this - the number of people who need to notice and attempt to a 51% attack is enormous ... and not possible to do after the fact

Before the fact? Sure - but then the 51% issue doesn't happen, and you get to precrime

Sure for smaller proof of work coins, and maybe today. It would require a massive amount of money, energy, coordination, and time - and it's getting harder to do as the total hashpower grows every day.

But who needs that?

If "they" can track you down "they" can arrest you, kill you, torture you, extort you, ...

There are ways to avoid your transactions being tracked. Coinjoin transactions, purchasing a miner for non-kyc bitcoin, payments on the lightning network, etc

Also, they can do all of those things, but you can setup your private keys in a way that your family will still have access to the bitcoin even if you are killed

"Lightning" protocol and other sidechains don't deliver on their promises as well as the base bitcoin protocol.

"Help" with privacy isn't enough, you need something that is bulletproof and either resistant to you screwing up the OPSEC or otherwise you have to get OPSEC right all the time.

Using the same mixer as terrorists could get you charged under anti-terrorism laws.

Before you use one I'd ask you to ask yourself if you want to be complicit in large-scale tax evasion, international sex trafficking and all sorts of awful things that make the mixer more than a game where you can imagine you're important because you're a spy or something.