Melee: Wah I don't get to use my LB for the 23490342 time! PARTY FOUL! PARTY FOUUUUL!!

In non-hardcore situations, it doesn't matter who uses it. Just be glad it's being used because most of the time, it's not. The LB isn't a melee-only button. ANYONE in the group is perfectly valid, and allowed to use it at any point they deem fit.