Masternodes are as centralised or decentralised as miners.
That is incorrect.
Decentralization is measured as the cost of the option to run a fully participating node (
http://www.truthcoin.info/blog/measuring-decentralization/).
In Dash, only Masternodes participate fully (IE, are able to access/verify/amplify the blockchain signal in a trust-free manner) and they have an entirely artificial, very high 1000 Dash barrier to entry.
OTOH, anyone with a CPU/GPU may exercise their option to mine.
what DarkCoin does is highly centralized
"masternodes" does not sound like something decenteralized, it sounds like something that creates a small chokepoint which could be used to deanonymize its users, like a server based CoinJoin but worse since you have to hold a huge pile of coins to run a server.
Unless they are a bagholding DashHole cultist, why on earth would anyone listen to your gainsaying assertions instead of a renowned BTC core dev?
In conclusion,
Your pump and dump dance would probably be more effective if you were less transparently dishonest in your approach.