I'm experiencing this exact same thing. One guy who I just flanked for the 3rd time while he was too busy looking through his sniperscope sent me a message midgame about it, telling me I didn't have 'the balls to use a primary'. My Lord of Wolves just ran out of ammo at that moment, so I started using my Paleocontact JPK-43 (which has a pretty nice roll indeed in my opinion), after the match I got another message from the same guy; '[i]You're garbage, absolute trash, that AR is OP and you suck for using it[/i]'. I had a good laugh and then further ignored those 2 messages.