There is a mod/patch that censors nudity, I think, though I can't precisely assure you this is true, it's likely just something made up, used to troll people bothered or offended by nudity and sexual content into playing the game. A twitch caster I follow was supposed to stream The Witcher using said mod/patch, but he never actually did, so I'm assuming it was a fake (on a side note, it had nothing to do with twitch.tv EULAs or anything, The Witcher series is on the list of games streamable on twitch).

You can't avoid all nudity, unless you find a censor patch. You can't avoid all sexual encounters (there's a scripted one, right at the beginning of the game, every other one is entirely optional and you are, in fact, able to skip them, but it requires some meta-game previous knowledge to do it 100% -- celibacy runs are usually only possible after you've finished the game once, so that you know how, where and with whom to avoid the sexual encounters).

I don't feel entitled to tell you whether you're right or wrong, it's a matter of your personal morals and beliefs, and though I don't particularly agree with them, I respect them -- and you. If you are offended by sexual content and graphic displays of nudity, then I think you should avoid The Witcher series entirely, because it is an intricate part of the lore and the background of Geralt, even in the books. If that censorship mod does exist, I hope some other user can let you know, but, otherwise, I think if you play the game you'll get more bothered by it than anything else.

Hope this helped.