I'm certainly one of those who likes to treat villagers very very kindly (considering I run a "rescue" town for abandoned villagers!), and I like playing the game with that as a focus. But I also fully understand those who sell, trade, and buy villagers. It's like Pokemon - I value my SS starter Feraligatr, my shiny Larvesta, and my traded 6IV Noivern immensely - even if each one came from very different places and for different purposes.
Even if I just wanted to complete my catalogue, have the prettiest town, or just get to know the different villagers, that's all part of playing the game. ACNL certainly encourages you to treat your villagers kindly, just like Pokemon does, but it also invites you to simply the game, with whatever purposes and emphases you want. I think it's alright for each of us to play the game we want. After all, the important part isn't the data within the video game, but the people involved with the video game, from creators to players. It's once we start stepping on their toes, or treating the real people poorly, that things truly get ugly!