Your thread wasn't breaking any rules, you're right. However, it was not discussion-oriented. Yes, you could have added a disclaimer telling people to explain their choice, but in my experience as a moderator such threads do not end well. They are prone to people posting ego-inflationary things, in addition to my previous explanation for why such a thread premise was a poor one to begin with (and as such precludes any discussion, including justification of said movie choices).
There is no discussion to be had in that thread, given the premise. It's purely pc++. What's worse is that most people's lives are a very poor fit to any film, considering how films are caricatures of real life.
This topic is actually under discussion in the moderator/administrator sub-forum and has been raised before. The main thought was that it was to be "pretty real girls" and not anime pictures, but as I said, its currently being debated.
I can't speak for the infraction, you'll have to talk to either the mod who gave you the infraction or an administrator. As for anime girls, Smogon historically has never allowed such things to be posted on our forums. The difference between that and the hot girls thread is, well, the hot girls are REAL, the anime ones aren't.