Before I do that (please consider I'm not a crypto developer, just a random user with cursory knowledge compared to you guys), could you even give a hint does it involve having 50% of the mining power as well?
No.
don't think I claimed it did. Anyone (with enough resources) could buy up all Bitcoin miners and do what ever he wants with them. Should I dump all my BTC asap?
Ok, so I'll make this easy to understand. Say I buy up enough bitcoin mining hardware to actually stand a chance at creating a double spend and I spend an equal amount of money acquiring masternodes. Is this situation equal from the attackers perspective?
The answer is no. Because I still have to use my bitcoin miners to outpace the rest of the entire network in order to build the longest POW chain. My masternodes have no such trouble, for them, creating a quorum is completely free of cost, therefore so is the attack.