It's only logical that the 51% group of holders will not have bad intentions against a currency that they themselves have a majority stake in.
For individuals behaving rationally in a closed system that is true. With entities that may have some overarching agenda, such as, hypothetically, the dominance of a competing currency, then the cost may be well worth while, despite "collateral damage", as it were.
The point is they are not so much attacking the currency as buying it. It's like instead of flying two 'planes into the World Trade Centre, the terrorists bought the towers and then shut them down so no-one could use them.
Bitcoin is more vulnerable to irrational attacks than PoS. They'd just have to kidnap the families of the controllers of the few largest mining pools. Or an ASIC manufacturer.
51% PoS stakeholders have every reason to reverse transactions. Because they use TOR, nobody knows they even have 51%. They can attack transactions to grow their wealth.
How will destroying trust in the currency increase their wealth, when that wealth is denominated in that currency?
With PoW, they have to invest in equipment that is traceable so they can't attack anonymously. When they want to cash out, their equipment is obsolete and worth much less.
You are being naive about how they need to acquire their equipment. Even if it is traced, so what? And once they'd used their ASICs to destroy one coin, they can sell it to other people to mine different coins (that use the same hashing algorithm).
Even with PoS you need to distribute the coins with PoW or you end up with horrible distribution of coins. The longer the PoW stage and more people having a coin, the fairer distribution. Hard to beat Bitcoin imo
Have you looked it the Bitcoin distribution? 0.71% of the accounts hold 55% of the coins. The real situation is probably worse, because each owner spreads their bitcoins over multiple addresses. For example, Satoshi rarely has more than 50 coins at a single address. We only know he owns millions of coins because he was the only miner for a while.
As for distribution of hashing power, that is also terrible, with pools sometimes going over 50% almost by accident.