We can do basically this today. I could probably do it, if I decided to throw my entire life away (which, if I'm considering killing, is the minimum bar anyway)

We can do basically this today. I could probably do it, if I decided to throw my entire life away (which, if I'm considering killing, is the minimum bar anyway) – though, not reliably and not without side effects. For an organisation of significant size, it's a question of how sophisticated they'd want to be. The main obstacle to your sci-fi scenario is that, to date, no such "contrarian gene" has been identified. In fact, most traits you'd want to genocide away seem tenuously related to particular alleles, at best. Unless we start seeing fanatical HERC2 purists, or the people making bioweapons decide they don't care about collateral in the War Against Redheads, we're probably safe from genetically-selective mosquito-induced heart attacks.