This very sincere and earnest question came from a childhood friend of mine, and oh my goodness, it just cracked me up! I've met this little guy, and he's got these twinkly blue eyes and an impish grin that just makes me want to muss up his hair and let him get away with anything. I bet he is absolutely gleeful about this new gesture!
"The finger" is a lot like swearing. It triggers an emotional reaction in some people - typically shock, aggression, or anger - and is therefore not something you want to see your child relying on for communication shorthand. On the other hand, we know that with some kids, our attempts to prohibit them from using it only inspire their creativity and determination to continue.
Here's how the talk went in our house:
Honey, it seems you've learned some new words at school, huh?
I'm not sure if you know that some people aren't bothered by those words, and some people get pretty upset when they hear them. Other people think that anyone who uses words like that must not be very smart, since they can't think of anything else to say. Of course, I know you are a smart guy, and can think of lots of other ways to say things.
So here's the deal: if you want to experiment with using that word, you can do it here at home with me whenever you want, since I am not offended by it. And when we have guests, or leave the house, since I can't be sure if the people who are around us would be offended or not, I'm going to ask you not to use it.
If you are not sure that you can remember not to say it in public yet, that's okay. When we need to go out somewhere, I'll just get a babysitter for you who is not offended by that word, and then you can stay home and say anything you want until you feel ready to try going out in public.
We never did need that babysitter. But your kid might be more persistent than mine, so be prepared to back up what you say! I predict it won't take more than once or twice being left home alone with a sitter (who has been instructed to be as boring as possible) while you all go out to the movies or skating or to dinner before he decides he can control it.
That being said, he may continue to use it with his little neighborhood buddies. I wouldn't worry about that unless they are offended. If so, then he may need to stay home for a while until he can control it. Same thing applies if he uses it at school - he may have to stay home or take a break in the office until he feels ready to control where he uses it.
The idea is to minimize the power of the word or gesture by not reacting dramatically when we hear or see it. When we get all worked up over it, we highlight it with our attention as something BIG and therefore quite interesting. Put it on the level of something like a burp or nose-picking. Socially offensive, but not a big deal. Your child will soon grow bored with it and move on.