I joined a PUG lobby you were in but I left immediately. I was the guy who said "Dude, your mic is really ****** loud" to whoever was talking with the mic inside his mouth. It wasn't you (talking) but I can't deal with that kind of ear-piercing BS. 
Affirmative. Sinful told buddy to try to fix it or turn the volume down and when he couldn't fix and didn't turn the volume down as requested by Sinful and the other guy, he told him to stop talking. He didn't comply, so Sinful muted him after first objective (pause game once out of lobby, select users name, select mute option. A feature missing from PS3 but thankfully is available for 360 because lots of faulty mics & other issues out there).
You should of stayed. The match started with 3 players total and Sinful forgot about the weight glitch fixing itself when another player joins mid-game. So Sinful ended up with 100% cooldown on Shaman instead of 200%. It totally ruined the enjoyment and effectiveness of his Melee/Biotic combo max recharge speed power evolution focus Shaman (only way he plays Shaman anymore). He badly wanted to quit that whole entire time because of this. As this was the main reason for the return to X-Box maxed manifest (super light weapon due to being maxed and omniblades). Only Sinful and the other competent player extracted. That guy with the bad mic and too much talking didn' (synced). He was also totally new to the game (level 3 common/starter weapons). If it makes you feel better.
So hopefully you remember this mute feature and stick around with Sinful next time someone mouths off non-stop on an extreme edition loud and echoing mic.