I wouldn't say it's wrong.
See, when people talk of discrimination against fat or non-standard girls, it's talking about a day-to-day basis, NOT the dating world. If you respect unattractive girls the same as attractive girls, you're fine. But if you're sitting and making fun of some woman politician's weight, that's crossing the line.
The girls who demonize you for your preferences are usually the ones who don't fit them.
And yes, I , like most guys, am attracted MOST to a specific body type. I prefer girls who are thin and firm. Like, a lot of guys seem to want girls who are thin, but at the same time have a back-breaking chest or whatever. I like more subtlety and smaller features, so a big chest is actually quite a turn-off for me.
Think Esperanza Spalding. She's just awesome inside and out.
Also, however, try to base your expectations on what you yourself can fulfill. For instance, I don't feel all that guilty about liking thin girls because I myself am a thin guy. But if you expect someone to regularly hit the gym or have a flawless complexion, you should be able to fulfill the same.
Too many hyper-sexual guys dislike hyper-sexual girls. Too many girls will talk about "too many skinny guys", but don't hit the gym themselves.
Only expect what you can give, and understand the efforts of others, and you'll be fine on the morality meter.