It could be that they're on a bad streak of games? Does not mean the guy is a bad player. Unless his combat record shows a sub 1.00 K/D ratio. But even that does not tell the whole thing. I played against this guy earlier today in a random lobby who was ranked 89 in the world or something his K/D was like .92 if I remembered correctly. Most likely a SPM player who plays alot of objective type modes and could care less about his K/D. PM can go negative a lot of the time because of situations everyone faces. Trying to get diamonds on a class they're not used to playing, bad lag connection. just typical bad luck. It happens.
I had a ton of bad matches when I was running only Snipers. I have never liked sniping, and I was working on getting all diamonds. I am sure I have plenty more bad matches to go running around with only pistols and the Ballista with Iron Sights.
Sorry some of us are trying to finish challenges and not carry you.