I'm going to call someone out at a barbecue.
Well now I am curious, what are you calling them out for?
He said something about me I don't like.
If you want to confront someone because you think they did something unfair or rude to you, it's best to do it in private. Doing it at a party will just make things awkward and uncomfortable for all the guests.
I'll do it anyway and I don't care.
You should care, because there will be a lot of people at this social gathering and they are going to look down on you for causing a scene. How would you feel if someone else came around and started randomly yelling at people with no context?