I feel this "nothing at stake" argument is being used without proof of its existence. Even though theoretically it's possible, but it also goes against human nature and logic. Why would you attack and destroy the reputation/value of the currency, that you hold an extremely large stake in? it makes no sense to attack yourself and destroy your own wealth.
From a "normal person's" point of view I'd agree - but from a "government's point of view" things change (as they can just print their own money as long as they wish).
So if a government wants to "destroy" a PoS chain then they can just buy up (paying more and more as they print more and more) and they will succeed.
In that case, it will cost the "government" much less to destroy a PoW chain. Also it might not even be possible to buy up 51% in a PoS chain if the coin is simply not for sale. But it's ALWAYS possible to get 51% in a PoW chain.
"In PoW even if a government wants to spend billions to kill of Bitcoin they just don't have the ASIC equipment to do so."
Why wouldn't they have the ASIC equipment? what's keeping them from obtaining ASIC equipment? I can see a variety of ways for them to obtain the equipment. If they want them fast, they can just offer to buy the equipment from current miners at a premium. If they have time, they can mass manufacture the equipment, easily.