I'm all for "play the game how you want & have the most fun." My issue with TTing is something like what Ian Malcolm said in Jurassic Park, "...it didn’t require any discipline to attain it. You read what others had done and you took the next step. You didn’t earn the knowledge for yourselves, so you don’t take any responsibility for it." That's fine in a closed system of play; may not be my cup of tea, but you do you.
However... when you bring it out into the community, it's:
1) an obvious advantage in any sort of trade situation
2) an obvious advantage in any sort of "I'm showing off what I've built, collected and accomplished" situation
Which are both fundamental aspects of the community. TTers can and do take advantage of non-TTers in the community. I don't think it's malicious at all, and maybe no one on either side of the equation are upset, but that imbalance is inherent, and ethically, it's a little shaky.
Aside from that, it's an obvious exploitation of technicalities that are not even part of the game, and the designers have openly stated they are opposed to it.