Sometimes things need to be said when you manage people
Being a manager is not an easy job. Sometimes difficult conversations need to be had. And they have to be said. Not saying something when it is required is far worse than speaking up. Your choice guides your team on the required and allowed behaviours. Allowing a behaviour which you don’t really think is acceptable sends a signal to the rest of the team.
So a direct message to that team member is crucial. It tells them what is required and tells the rest of the team what is required. And it tells everyone that performance matters and you won’t let it go.
So if you see something that you don’t think is part of what you want your team to be, say something.