The greys amongst themselves

Did you ever receive advice from someone you can give advice to? A smoker telling you to stop drinking, a cheating partner telling you to be honest at work, a harasser telling you the importance of family bonds.

It seems that some people express a need to change those close to them so that they become similar; but why? It's not necessarily the saintly trying to guide the doomed to salvation, it is those in between that want to form a big homogeneous blob and fervently hammer any nail sticking out; but why?

I mean, sure, there are some observable difference but they are usually on the surface; if you dig down to morals, values,  and beliefs you must find a consonant entity or risk ostracism.

Where do these people get the nerve to stand on moral high ground while also holding very contradictory values? Cognitive dissonance is the uniquely human ability to hold two different beliefs that are contradictory to each other e.g smokers that acknowledge the adverse health effects of smoking but do not quit and wish for a long life; but still why must we conform?

We were not raised to accept that which is different so we huddle and homogenize until we all walk, talk, eat, fuck, and think the same. Why?