That Louie is a cutie!! If you have had lots of people over and he has never done this before...I would agree he just didn't like these particular people for some reason (and maybe a good one). And it could have been the shoes, my Cooper doesn't like my husband or sons to wear baseball caps and he will take them off their heads every time and then hide them
Anyhow, I wouldn't worry about Louie being agressive unless it happens again. Did they talk to Louie at all or just ignore him?