I like Cool's take on having multiple faces, it's fine to have different faces for different people as long as they are all genuine, but some people and manga have tried to portray the opposite like you can only have one face ever.
Friend A may not like the same types of jokes as friend B so you don't tell them around friend A, that means your being considerate of friend A not lying or being disingenuous. However putting down the things you love just to fit in with friend group C is lying to them and yourself, that's when it becomes bad if only for yourself.