So these guys at poloniex wrote that BCN deveopers have some keys that can be used to destroy some specific coins anytime - and you're ready to believe it? Sounds absurd to me.

Firstly, it totally eliminates the economy that has been developed - people had bought and sold, made money by creating services - then all of a sudden their coins are just taken from them?

The developers of any coin would never do anything like that, no one would trust them at all afterwards.

Secondly, what is this idea of top-secret keys no one has heard of?

Several forks of bytecoin have been launched - this type of keys would have surely been mentioned somewhere already.

The basics of the whole philosophy of cryptonote and bytecoin is decentralization and anonimity - there cannot be such a thing as a secret key to destroy coins.