If its 50 minutes into the game, and our AD carry is about to die. Only way to save him is by taking the kill on their Riven. I take it.
If they bitch to me afterwards, I just call them stupid, and mute them. "Oh no 1 less kill to showoff my inflated ego with" Shut it, winning is more important then kills.
I steal them so the enemy knows who is the real boss in our lovely relation w/ my ADC
I steal kills constantly to save people. Then they bitch and whine about how I KS'd. I just reply, you're welcome.
I take all the kills, every single one of them I can get. If my adc DARES to complain, I point out how impossible it would have been for them to get that kill alone. I also point out how much safer I can make their laning phase by having that extra gold. If they sass me back I offer to share the kills if they share some of that tasty looking farm, then drop my entire mana bar taking a wave. Show them who the fuck is running this shit down here. If they rage and abandon lane to suicide to gromp, I just farm up my
.
We all know who the real carry is down here anyway:

I say, there is no KS. You get what you earned. I just want the enemy champ to die. I don't like getting them down to 2 hp and no one gets that final kill shot because I leave it for them. If it is there to take, I take it. Get over it and kill someone else.
"Oh, you're running away with a sliver of health? Let me just drop this E under your foot"
Peasants, please. If you're farming minions and never taking the time to poke the enemy and leave it all to the 0 cs support, all to buy those damage items you never use unless you all-in in a teamfight after grouping mid for fifty minutes and not doing anything, don't be surprised when it's revealed that they can get more shit done than you with no real gold income.
Supports aren't personal servants, nor will they act like one. Because who wants a collar slapped onto them by a little bitch? Now that's just irony.