I can think of another reason for lying to kids: because everybody else does, and if your kid doesn't play along there are consequences. I am reminded of Roman Polanski, who was Jewish but was raised Catholic at an early age to protect him from the Nazis. He ended up becoming an actual Catholic, because you can't tell a four year old that he's really a Jew, but has to pretend to be a Catholic, because they're incapab…
If you don't think there's anything wrong with swearing, you don't have to say "You can't swear because it's wrong." You can say, truthfully, that there are certain words grownups are allowed to use that children aren't. You can say "You are not allowed to say that because if you accidentally say it at a friend's house, his parents won't want you coming over to play anymore." That's very likely true. You may be leaving some things out -- reasons that you don't fully understand and therefore don't know how to explain to a small child -- but you don't have to actually tell any lies.
You don't have to believe in religion to teach your children that you respect other peoples' beliefs, and don't try to correct their religious beliefs when you don't agree with them. Of course, if you actually think they're stupid for having those beliefs, then you will have to lie by omission to help their social life. I haven't told my children any more than they asked about my beliefs, so it took until my daughters were about 10 until they realized I don't believe in God at all, but I didn't lie or pretend to believe something I don't, either. They understood from an early age that different people believe different things for a lot of reasons and it's only polite to respect that.
If your kid is curious enough to ask questions that can't be answered without explaining the mechanics of sex, you can also teach him that we don't really talk openly about sex in polite conversation, and that other kids might have parents that don't want them to know about it yet. And remind them that it's important to them socially that they don't get in trouble with their friends' parents.
You can say that George Washington Carver's achievements were not so much scientific as social (and you don't entirely understand why they're learning about him science class), without saying that no black scientists are worthy.
This is the approach I've taken, and it's worked pretty well so far. We live in a very "Christian" suburb, and so far my kids haven't been kicked out of any homes for being inappropriate, nor have any of their parents come to me with concerns about such things. (I have 16 year old daughters and a 6 year old son.)