Is hypocrisy a sin, negative vibe, whatever? Has your church/temple/group..

[cbayer]

1. Definition

a feigning to be what one is not or to believe what one does not; especially : the false assumption of an appearance of virtue or religion

I'm not aware of a list of specifically designated sins, other than breaking the ten commandments. I suppose it could fall under:
"Thou shalt not take the name of the Lord thy God in vain"

Anyway, if purposeful, it's a lie and I think most would agree that that is not a good thing.

What your BIL references is the following:

Matthew 7:3-5
New International Version (NIV)
3 “Why do you look at the speck of sawdust in your brother’s eye and pay no attention to the plank in your own eye? 4 How can you say to your brother, ‘Let me take the speck out of your eye,’ when all the time there is a plank in your own eye? 5 You hypocrite, first take the plank out of your own eye, and then you will see clearly to remove the speck from your brother’s eye.

which is a "people's in glass houses" kind of directive.