This game is not realistic, you do not respawn if killed in reality. So the whole its not realistic card is just a failure on your part.
Stop being a mindless rusher getting to close to them and then as soon as the animation begins to change start to move away thinking they are dead.
And pay attention each match to who goes in to FS and watch the leader boards to see how many times they have died. So if you get near them you have an idea that they could drop in to FS the next time they die. So if they do you can react to it properly isntead of just getting butthurt that they ended your precious kill streak.
Final thing, stop taking this game serious, it is just a game meant for entertainment and nothing more.