The reason this topic was made is because, obviously, to the OP, it is questionable. If it wasn't questionable to him/her, he/she would not've made this topic to ask the question.
Now, Metagross evolves from a swarm pokemon. As well, it is genderless, and has no egg moves. It would have been easy to breed with a Ditto, with no consideration needed for egg moves.
The hacker was dumb, because they hacked so obviously. What you did wasn't necessarily dumb (or at least it won't seem so until you're judged and thrown into the lake of fire), but it did continue a cycle that you wish had never started. Either you recieved a trade from a hacker or from someone of the same mindset as yourself. It's kinda like the line from the first Charlie and the Chocolate Factory: and so shines a good deed in a weary world. Meanwhile, all deeds of other nature don't.
Releasing or using the pokemon in-game would've not been so questionable. Breeding it would've been fine for the most part, due to random number generators generating numbers randomly (RNG, GNR). Trading it is very much questionable, as would using it out of game.