@garythegengar
Your argument is good, but the main point I disagree with you on is the list of sect's checks. You listed "spdef tyranitar with fire blast, full health band terrakion in sand, heatran, or the blobs". Let's add to that:
gastrodon, rain rachi, tentacruel, rotom-w, rotom-h, any somwhat bulky fire type (ninetales, volcarona, victini, any of these could run some SpD investment), kyurem, kyurem-b, quagsire, virtually any steel type in rain (aside from rachi, there's metagross, bronzong, even SpD skarmory), even something like empoleon. Several of these pokes lose if genesect runs a specific niche coverage move--giga drain for gastro and quaggy and rotom to an extent, flash cannon i guess for kyurem, tbolt for empoleon--but these all take a valuable moveslot and prevent genesect running moves it absolutely needs to, ice beam and flamethrower being the two most common.
Furthermore, there are many pokemon listed above that check genesect absolutely, such as the blobs, heatran (no one runs hp ground), steels in rain, SpD fire types, and others. Although genesect is a potent sweeper, with a list of checks this long, I honestly see no reasonable argument to ban it. I've made this comparison before, but look at terrakion. The number of pokemon I can think of that can take a +2 LO CC or SE is like skarmory (not really, dies to CC with SR damage), gliscor (and if terrakion runs air balloon or rock gem, it has no chance), slowbro (2HKOed), and tangrowth (2HKOed). That is way way scarier to me than an RPsect.