There have been a couple threads on this with some good information if you want to do a search. The basic info is that everyone is different and people are at different levels with how they feel about their speech. Generally, you want to let them say what they're saying without filling in words or finishing their sentences. its common courtesy. Some people don't mind if people help them out; it depends on the person. You dont need to treat him like a sad puppy. My advice is treat him like you would any other person and don't worry about it too much. The more one of you worries about it, the more the other will probably. Oh, and if his parents gave him a name with any other letter he'd probably have a hard time with that one too.