The only people that complain about MRT's are those that get rimmend by numbers, so if you want to prove to the mods that MRT tribes shouldn't exist because they aren't needed, then take a stand and fight 100-200 players, prove your point that all MRT are bad. Also, that merger happens when tribes are tired of playing that world and wish to move on to other worlds, when a world drags on for months on end, then size really matters, and endgame can be achieved faster through those mercy merges.
The world is SUPPOSED to drag on for months on end guy, this is tribal wars, not a 15 minute match of SC2. My first tribal wars experience on W4 of Tw1 (Which btw, I was in the tribe that won the world, a MUCH bigger accomplishment than a world winning tribe on TW2) dragged on for four years. We NEVER merged with anybody, for the most part the same players that were there at the very beginning were there at the very end.
"Mercy merging" as you put it, is nothing more than a poor excuse that players like you push to make it seem like what you're doing is something benevolent, when in reality you do it because you're scared that without a massive zerg of other players to hide behind, you would start looking like a mighty easy target due to your lack of skill at the game.