Smurfing is fine IMO
My actual smurfs are the same rank as me MGE / DMG. However I need low rank smurfs as I have adopted 5 silvers. I can't play with them on my accounts due to rank difference and even if it's a full party what is a silver 2 going to learn vs DMG, probably just to hate the game.
So to help teach my adopted silvers, I need low ranked smurfs. As Kuno said, yes it's a team game but some people just paly it for a laugh as were the 4 people I played with last night. They didn't want to work as a team or even go anywhere but rush long, so utterly pointless to try at that point. Better to lose and enjoy myself rather than full on try hard and get frustrated.
If you got a group of tards that werent gonna win anyway cause they dont communicate and just pro90 long all day its fine to mess around and go deagle or scout only or something so you actually enjoy yourself.
But if there is 3 people actually trying (within their skill level) I don't think it's fair to play poor on purpose.