Avoid them?

Is Paul really telling us to shun people? 

Romans 16:17-18(NKJV)

Now I urge you, brethren, note those who cause divisions and offenses, contrary to the doctrine which you learned, and avoid them. 

For those who are such do not serve our Lord Jesus Christ, but their own belly, and by smooth words and flattering speech deceive the hearts of the simple. 

One of my problems with this passage is that it can too easily be misused to crush valid disagreement.  Let's take Martin Luther for example.  He caused divisions and offended some.  But he also turned out to be correct.  Should he have been shunned? 

Or how about all of those people who refused to believe the earth was flat.  The church used to burn people at the stake who refused to believe the earth was flat.  The round earthers were proven to be correct.  Should they have been shunned?
 

Just wondering.