Well, lets mull over the comment and clear up any confusion you have.
I’m talking about the spirit of competition, due to how PvP in itself is competitive in nature with obvious fail/win states. Their exist a spectrum of levels of competition for PvP itself. At the bottom is obviously World PvP, up next is the Casual PvP, then you have your Ranked PvP, then of coarse, E-sports. Their exist more of coarse that i haven’t listed. The rewards also exist in a spectrum respectively following the types of PvP. World PvP Rewards World PvP related rewards, Casual PvP Rewards Casual PvP, etc etc. And of coarse the tension follows that rule as well, and sometimes theirs more win and fail states then just kill or be killed (which it is a primary, often mandatory goal of PvP).
The metaphorically rule of thumb for a game (that those are also competitive in spirit) cooperating with a team to win said game, is to not screw with your team’s win chances. Even if game is easy, the competition is still there to balance things out naturally, and if your somebody on your team is doing everything they can to self sabotage their own team, that easy game would become harder for often times no reason.
To help you understand better this, lets use Highschool Football as an analogy, which is appropriate comparison to a video game’s casual PvP Match. You have a team that is a bunch of Jocks and the other team is the Nerds. (Yes, that’s how highschools work back then.) One of the players, we’re going to call him Billy the Goat 
(cause his mouth and insides are so strong that he can literally eat tin cans and license plates, and can climb up 85 degree dams), decides to pull some pranks or just do stuff for a laugh. That being tackling their own team member kicking the ball out of bounds, scoring the wrong goal, delaying his actions intentionally, replacing the coollade dispenser with liquid cheese… You name it, and claim that the other team should watch out where their going or excuses like that. What should be an easy win for them turned into practically the first ever loss for them because of Billy intentionally sabotaging their team’s win. Then the Coach kicked Billy off the team and made a new rule that anybody who does what Billy does will be kicked out, no second chance. 
The problem wasn’t the difficulty of the game, but the team member(s) maliciousness, has made the wining of said game’s chances much harder or completely destroyed it. And cause of Billy’s fun at the expense of the team’s fun, he has set the rule whether he intends to or not, that basically make the team as well anybody else who join in the future to walk on eggshells.
I hope this answers your question. 