Well, MRD doesn't necessarily do more DPS than a war (my MRD will NOT do more DPS than my WAR, for example). Yes, even counting Raging and BfB. The stats on the soulstone add a good amount of base damage which MRD doesn't get, and if you have a properly statted relic there's another advantage to staying war.

Ultimately, it depends on your attitude. If you're snapping at people wondering why you're on MRD, then you will deserve to be kicked. If you're saying you can do more DPS as mrd and get out dpsed by a pld...while they really don't have much of a ground to kick you, you are likely costing the party more by being just...bad. And if your tank went down or was new and you couldn't tank propely...yeah, that could be seen as harassment