Where there’s anything that’s not correct, whether its just outright incorrect behaviour, or a bid’ah, then there’s an adab (manners), in how you deal with that.
That you can find in works that deal with Enjoining the Right and Forbidding the Wrong, the first of which is that you have knowledge of it.
The second is that it is such a clear matter that everybody knows it is a bid’ah. Now you have people who see a tiny little thing and they say “Oh no no, that’s a bid’ah!”. It has to be something absolutely clear.
And then you have to have manners in how you deal with your brother or your sister. You can’t go up and harangue them. You dont do it in public; you don’t go and disgrace them in front of others. You find a sweet way to deal with it.