I've been off Chi'as since girlhood, when I visited a friend's house. I expected to get a nice hello from the family, but what I got was two mean and hysterical chi'as whom nobody could control.

Since then, I've read a book by a vet on how to deal with that. Basically, a dog hates to be excluded from a party. If a guest comes and your dog is aggressive, collar the dog and shut it up in a room. When it calms down, let it rejoin the party. If it acts aggressive again, shut it up again.

Repeat cycle until the dog figures out that its "I hate visitors" act means that it gets left out of the fun.