I don't find anything wrong with copying other teams. The only thing I would say that wuold be (slightly) against it is that you kinda lose the pride in winning a good match or a clean 6-0. I mean, sure, you did it and mayeb the original poster couldn't have done so vs. the same person, but knowing that the team wasn't built from scratch (or a small base) and by yourself with moderate help (RMT forum ftw), it's basically like saying "I don't have the initiative to learn competitive pokemon, I'll keep using this sweet team that works all day long and not build another team out of it with my own ideas."
I take more pride in winning with my team (I Rest in Peace; You Rest in Pieces) than I did when I win with the Ubers team revolving around how useful Garchomp is in Ubers (forgot name lol; it's in the archive I know that much. Might I add I played Ubers before I went OU). Contrary to everything I've said, I did learn from that team: I realized that building a team that revolves around one pokemon, even choiced or frail or not even super-powerful or fast, can be incredibly effective, and thus arose my RMT revolving around Heracross. And with the help of raters here, my team has been avidly improving since I started with it.
Copying is perfectly fine, IMO, but you have to understand that using that team you copied should be used to help you learn, not to just contiously use and brag about it (as if there is much to brag about copying a team lol).